The Everett McKinley Dirksen United States Courthouse and Federal Building is a slender, monolithic, thirty-story structure. It is one of the three main components of the Chicago Federal Center which includes the forty-two story Klucynski Building, and the single story United States Post Office, all designed by Mies van Der Rohe between 1959 and 1964. The complex is a cohesive integration of outdoor plaza space and progressive architectural form that corresponds with the grid of the Chicago's urban core. The buildings frame a 4.6 acre plaza, which was also intended as a setting for public art. Alexander Calder's Flamingo was installed in 1974 as the final accent for the Federal Center. Mies van Der Rohe used light gray Rockville granite to pave both the open space and the lobbies of the three buildings to create continuity between interior and exterior and yield the impression of placing the buildings within an expansive outdoor room for the Federal Center.
The Dirksen Building is sited on a north-south axis, and stands on the east side of Dearborn Street. It offers both east and west views and establishes the western edge of the Federal Center. The Dirksen building stands 368'4" feet wide and 363 feet tall, making it virtually square in proportion as viewed from the public plaza. It is 13 bays wide, and 4 bays deep - a depth of 116'4" - yielding a narrow profile from the side view. The east and west facades have thirteen primary bay divisions, mostly discernable from the base of the building. The bays occur between fourteen steel columns that encircle the perimeter of the building.
There is a smaller scale plaza to the east of the building, which appears as a more private space, although clearly is a feature of the overall site. It is accented by several low-scale rectangular granite planters of the same Rockville granite of the plaza, which continues to form the interior floor of the main lobby. The same granite - differentiated by a flame finish - is used for sheathing of the elevator core. The granite provides a durable finish and is one of the most important materials defining the very essence of the Dirksen Building.
The primary exterior characteristic is a curtain wall design comprised of steel I-beam mullions that are affixed to the structural steel frame at each floor level. The mullions separate expansive panes of gray tinted glass. The transparent curtain wall continues upward to the twenty-seventh floor, where there are louvers rather than glass. Visually, this change alters the solid to void ratio of the facade, creating a transition that terminates the height. This transition correlates to the fact that the top three floors contain mechanical rooms and equipment, rather than being occupied tenant floors. While the exterior tends to exaggerate the vertical dimension, the horizontal floor structure is also articulated and visible behind the plane of the curtain wall mullions. The horizontality is therefore more subtle and only readily apparent from a distance. The rectilinear forms still clearly reflect the structural geometry that is the signature detail of all van Der Rohe buildings.
A flat, cantilevered canopy articulates the primary entrances, centrally located on the east and west elevations. The ground level lobby is a monumental, light-filled space accented primarily by the gray Rockville granite floors, and the polished granite sheathing on the walls that enclose the elevator cores. These internal cores are symmetrically located within the lobby. Entrance to the building is through stainless steel revolving doors located symmetrically around the perimeter of the lobby, and a series of paired doors. Two of the entries have been altered (one each on east and west walls) to accommodate modern accessibility requirements. Within the lobby, steel columns, identical to those on the exterior, evidence the structural support and the dimensional modules that determine the dimensions of the building, and that are the basis for the plan and layout manifested in all of the upper floors. The lobby, at the ground level, is a two story volume contained by a transparent glass wall set internal to the perimeter columns, creating the sense that the upper mass of the Dirksen Building floats above the ground. The glass wall is articulated by narrow steel mullions, which are set at a 9'4" spacing, double the 4'8 distance between the mullions of the upper facades.
Typical of all of van der Rohe's designs, the footprint of the Dirksen building is based on the specific geometry of dimensional modules. The column spacing seen most clearly in the lobby shows a 28 foot square grid that represents the internal dimensions throughout the building, down to the office sizes, corridor widths, and ultimately depicted on the external curtain wall. Using the module as the basis of the design, no dimension or feature of the building has an arbitrary dimension. This extends even to the controlled spacing of the original ceiling tiles which are placed so that a wall could be inserted at the 4'8" interval between the tiles. Floor to floor height is 12 feet.
SIGNIFICANT FEATURES/SPACES: The following features/spaces are notable and pertinent to the architectural significance of the building.
Curtain Wall and Exterior Skin: The exterior curtain wall skin, and the steel I -beam mullions define the rectilinear image of the exterior. This curtain wall system is the most prominent attribute of the building, and is the feature that accentuates the verticality, is intended to represent the structure of the building, and typifies the high-rise architecture of Mies van der Rohe.
Ground Floor Lobby
As described above, the main lobby is an expansive two story volume, contained by transparent glass walls. The space is punctuated by the square, black, steel columns that support the load of the building, yet are also a focus of the lobby area. The lobby ceiling is flat plaster, painted white, with recessed lighting placed in a precise rectilinear pattern. The floors and the walls of the two elevator cores are gray Rockville granite, articulated by a rectilinear scoring pattern that is not readily apparent due to the surface texture. The only substantial modifications impacting the character and appearance of the lobby are the expansion of the information desk, and the addition of security screening stations. Butt-glazed partitions have also been added to demise the open lobby space into zones of security related to the screening location. Although intrusive, they remain subordinate to the main architectural elements of the lobby.
On the west side of the building, the corridors are notable for their width and openness - which is fully appropriate to their function as the main circulation spaces. The strongly rectilinear building plan is comprised of two corridors running north-south, connected by the short transverse corridors at each elevator core. Opposite the elevator corridors along the west wall of most floors there are open "sky lobby" seating areas, offering a view over the Federal Center plaza. Carpeting has been added in all cases over the original linoleum. Several floors now have textured wall covering that changes the perception of these corridors space from its original unadorned painted plaster finish (particularly floors 3, 4 and 5). Typical corridors are double-loaded, opening to private offices located on the exterior walls. The service core, support facilities, and restrooms are accessed from the internal walls. Ceilings feature the acoustical panels, placed regularly along the ceiling, perpendicular to the length of the space. The placement of the ceiling tiles and light fixtures are fundamental to the design of the interior spaces and based on the increments of the 4'-8" building planning module. Throughout the upper stories, the main corridor walls are of painted plaster, accentuated by original steel door frames along either side.
On the building's east side, the corridors are narrow and used for internal "staff" use, never intended to be heavily utilized by the public. Original materials are also evident, including applied acoustical ceiling panels, light fixtures and original signage.
Elevators and Elevator Corridors
Transverse corridors that are 9'6" wide provide access to banks of elevators at each end of the building, located between column lines 3-4-5, and 10-11-12. Ceilings on the first floor have a suspended metal grid providing continuous reflected lighting, similar to the luminous grid design found in the original Mies van der Rohe courtrooms on the upper levels. Floors one and two each have two corridors at each end. The remaining upper floors have only one corridor, located between columns 3-4 and 11-12. Originally the corridors featured painted plaster walls, broken only by the very plain steel frames of the elevators and other closet doors - all painted in a gloss black finish. In 2003, almost all of the corridors (expect as noted in the following section) were sheathed with a polished granite, with the intent of formalizing the character of the building. Introduction of the granite on the majority of the floors is a dramatic change from the stark appearance of the original design. However, the steel frames of the elevator doors are still in place and the original design is evident. The applied granite sheathing is a reversible condition should it be warranted by a future restoration.
The original courtrooms are paneled in a stained walnut, creating a formal impression and presenting a dramatic departure from the starkness of the corridors. The courtrooms are further distinguished by a suspended, backlit, lighting grid that obscures the light fixtures and creates the impression of a luminous ceiling providing natural light. The rear walls feature vertical battens that provide sound buffering for acoustic purposes. Judges benches, tables and furniture are original furnishings designed for the space. All of the courtrooms are two stories in height.
Second Generation Courtrooms:
The initial expansion of court space occurred on the 14th Floor. Four court rooms were completed in 1994, designed by Dirk Lohan, Mies' grandson. These courtrooms are clearly derived from the initial Miesian designs. They feature walnut paneling in a coffered pattern created by raised moldings, and a suspended luminous lighting grid in the center of the ceilings. Many of these minor deviations from the original architecture are in response to modern courtroom technologies for presentation and sound reinforcement. Other features are similar to the Mies design. These courtrooms are significant because of Lohan's relationship to Mies, both as a relative and as a practicing architect. These courtrooms are notable in that they follow the intended allocation of the space and utilize the internal flexibility of the building envisioned in the original program. The structural framework was designed so that the floors could modified to accommodate courtroom expansions over time.
The combined Courtroom of the U.S. Court of Appeals, and the U.S. District Courts is at the center of the 25th floor. This courtroom occupies the two central modules of this floor, and is a two story space. Dimensionally larger than the other court rooms, it features the walnut paneling and luminous suspended ceiling. Accent fixtures include a clock, symbolic medallions for each court, original judge's benches, furniture, and gallery seating.
Third Generation Courtrooms:
In 1998, four additional courtrooms designed by Urban Design Group were created on the 12th Floor. These are notable primarily for representing the internal expansion of the court function within the Dirksen building, but are a departure from the architectural language of the Mies courtroom spaces.
Original Mies-designed courtrooms are located on the perimeter of several floors. They feature walnut paneling on the primary wall behind the judge's bench.
Judges Chambers are located at the eastern wall of floors 17, 18, 19, 21, 22, 23, 25, 26, and 27. Chambers include a Secretary's office which is the primary access, the Judge's main office, a private study, and private restrooms. They are finished with the standard features of the building - lighting and acoustical ceiling panels, and are distinguished by the full height windows along the outside walls. Although the planning and architectural features and finishes are predominantly original, much of the character of these spaces is derived from the furnishings and appointments as provided and influenced by the individual tastes of the occupants.
Prisoner Holding Cells and Circulation, 24th Floor:
The 24th floor contains the US Marshall's office, including a row of prisoner holding cells along the east wall. They are accessed through the Marshall's Office, and also are reached through a separate elevator from the basement level that can stop at all the courtroom floors, so that there is full prisoner separation throughout this high rise structure. The cells are created with chain link fencing, and have ceramic tile walls, and aluminum bench seating. These are not notable architecturally, but are historically significant as evidence of the integration of prisoner holding and circulation function as an aspect of the judicial procedures required in a courthouse, especially unique in a high rise situation. Accommodating prisoner needs and separate circulation in a high rise structure is potentially unique to the Dirksen Courthouse, as well as the related needs for establishing prisoner containment, circulation, and separation from Judges, court personnel, jurists, and the public.
Elevator Lobby renovations on most floors - new granite sheathing on corridor walls.
Renovation of the Dining Areas and Kitchen on Second Floor
Insertion of staircase, west wall, floors 3, 4, 5
Four new courtrooms added in 1994 - floor 14. Designed by Dirk Lohan
Four new courtrooms added in 1998 - floor 12 Designed by Urban Design Group
Carpeting installed throughout all corridors
Various modifications to the floor plan on floors occupied by non-court tenants
Elevator cabs have been renovated are no longer authentic.
PRESERVATION ZONING PLAN DEFINITIONS - INTERIOR
Zone 1 - Restoration Zone
This applies to interior spaces that display original architectural form, features and materials that define the original design intent and architectural character, inclusive of all building components. Modifications in a Restoration Zone have been limited to minor maintenance or replacement of finishes over time. These modifications do not significantly alter the original interior finish palette, and are not considered intrusive. Minor infrastructure and utility additions and/or modifications, such as security cameras, thermostats and emergency fire horn/strobes, are considered minor and acceptable. In addition, Restoration includes spaces where the current use is still consistent with original function. This would apply equally to ceremonial and public spaces, such as lobbies and courtrooms. In certain situations - notably the modified elevator lobbies - the Restoration Zone designation is applied to locations that regardless of their current integrity, could - under ideal circumstances - be restored to their original appearance.
Zone 2 - Rehabilitation Zone
While the original space and function may be intact, in the Rehabilitation Zone, some of the original finishes have been changed. Typically Rehabilitation includes corridors and open office areas, where flooring, wall and ceiling surfaces have been modified, but the floor plan and configuration are evident - including ancillary offices and courtroom support areas - where a specific secondary function is intact. Modification of these areas should still retain any character defining features.
Zone 3 - Renovation Zone
Renovation Zone applies to interior spaces that have been significantly altered from the appearance and finishes of the original design in all aspects - including floor plan, function, and materials. Most, if not all, of the original architectural character of the space has been altered, and is no longer identifiable as "Miesian" in any tangible sense. The Renovation Zone also includes areas that are purely utilitarian, generic space, without architectural expression, and are not contributing to the architectural character of the building. This includes mechanical rooms/floors, internal fire stairs, and other functional/service spaces.
There are some office floors which have been demised in such a way that the open character of the original floor plan is lost. Additionally, Courtrooms that were added in the most recent phase of construction and not based on the original architectural vocabulary are considered Renovation Zone.
PRESERVATION ZONING PLAN DEFINITIONS - EXTERIOR AND SITE
Zone 1 - Restoration Zone
The Exterior Restoration Zone includes the exterior glass and metal curtain wall system, ground level exterior perimeter arcade, and site features and organization. All aspects of the curtain wall system, including exterior and back-up structural components, glazing, color and construction are to be considered as within the Restoration Zone. Exterior soffits, lighting, signage and entranceways that are part of the building enclosure are also included. Original site furnishings, including benches, planters, guardrails, and flagpoles, site materials such as plaza pavement, metal area way gratings and drainage trenches also fall this category.
Zone 2 - Rehabilitation Zone
The Rehabilitation zone includes exterior elements include building materials and/or assemblies subject to periodic replacement and maintenance, such as the roof membrane. These systems are not unique to this architecture or and design, and represent commonly acceptable construction techniques of the era of original construction.
Zone 3 - Renovation Zone
The exterior Renovation Zone includes new and non-conforming site features such as security bollards, which were not part of the original site design and were not programmatic requirements at the time of construction. Some of these modifications have been recently constructed.
FLOOR BY FLOOR INVENTORY - DEFENDING THE PRESERVATION ZONES
The curtain wall and window assembly is a character-defining aspect of the building is categorized as a Restoration Zone that encircles the external perimeter, and includes the interior components of the curtain wall system, regardless of the zoning designation of the adjacent internal space.
The public spaces are more important to retain and potentially restore than the "private" spaces in the Judge's Chambers, and the more generic level of office space. In many cases, the public corridors are Restoration Zones, yet the adjoining internal office space is a Renovation Zone, since internal alterations of office spaces, or relocation of demising walls would not impact the appearance of the public corridors.
The elevator corridors have been uniformly modified throughout the majority of the building. They are depicted as Restoration Zones because they are public areas that in the context of a future building-wide restoration could be returned to their Miesian appearance. Locations where the corridors are original are noted below, and identified on the individual drawings of each floor.
On the floors that are primarily designated as Restoration Zones, this designation is intended to formally note the architectural integrity of these floors, and to encourage that future improvements be contained within the private offices.
The elevator cabs in the primary public elevators, while modified, are included as part of the Restoration Zone, since they could be restored in the future to more closely match their original appearance.
On certain floors the restrooms remain in their original configuration and retain the 1964 fixtures. These restrooms are defined as Rehabilitation Zones, primarily to distinguish them from restrooms that have been modified to meet ADA requirements or have been otherwise upgraded from the original. There is no intention to preclude future alterations as may be required by code.
Areas that are purely "service oriented" such as utility closets, mechanical rooms, fire stairs, and other functional spaces are designated as Renovation Zones throughout the building.
RATIONALE FOR ZONING PLAN, INDIVIDUAL FLOORS
Ground Floor - The Ground floor and the entirety of the Federal Plaza is a Restoration Zone due to its authenticity as well as its vulnerability to changes. The lobby is a major "character defining feature" - significant as the main entrance and gathering place for both tenants and visitors, and therefore is the primary public space of the building. Architecturally, the lobby is a key aspect of the stylistic image of the Dirksen Building and its integration with the plaza. The ground floor and lobby convey the interface between "interior space" and "exterior plaza" that is a fundamental aspect of the design of the Federal Center. The minor exception to the Ground Floor designation is the service core adjacent to the elevators, which is utilitarian space, and uniformly defined as a Renovation Zone.
Second Floor - The second floor is a quasi-public floor, the majority of which is a Rehabilitation Zone, due to the large amount of space that accessible to the public. Most of this floor was intended to be open space that has been infilled over time, but which retains a strong semblance of its original appearance. The kitchen is a designated Rehabilitation Zone since it is a utilitarian support space, and not a public space. Original ceramic tile wainscot and ceramic flooring are still in place throughout the kitchen area.
This floor also contains the main employee dining room and private dining rooms for the judge, quasi-public areas which are all designated as a Restoration Zone. The main dining area has been modified by the insertion of all new finishes which fundamentally change the appearance and character of this space. New dropped ceilings and light fixtures are no longer Miesian in appearance, including new indirect lighting which creates a continuously luminous ceiling plane. These design changes have an impact on the appearance of the building from the exterior and the general perception of the architecture from the plaza. A future restoration could recapture the original characteristics of these important spaces.
Third Floor - This is a Renovation Zone. This floor was originally designed as open tenant space. Interior fit out work would have been subject to the original building standards, including ceiling and lighting design, doors and frames, and floor specifications. This floor (with floors 4 and 5) was remodeled and reconfigured in 1992 into private office space for a single government tenant. There is no public access to this floor. Private offices are situated around the entire perimeter, and open office cubicles line the corridors. The overall rectilinear plan relates to the original intent, but the finishes have been substantially modified. A new staircase inserted at the center of the west elevation connects floors 3, 4, and 5. This is not a historic feature, and is not sympathetic to the original architecture. Future changes on this floor would not have a discernable impact on the integrity of the building or any notable features, with the exception of any interior architecture that would influence the character of the building as perceived from the exterior. (Note that the new stairway is readily visible from the plaza.)
Fourth Floor - This is a Renovation Zone. Similar to floor 3, this floor was remodeled and reconfigured recently in 1992 as private office space for a single government tenant. There are private offices around the entire perimeter, and open office cubicles in the corridors. There is no public access to this floor. The overall rectilinear plan relates to the original intent, but the finishes have been substantially modified. A new staircase inserted at the center of the west elevation connects floors 3, 4, and 5. This is not a historic feature, and is not sympathetic to the original architecture. Future changes on this floor would not have a discernable impact on the integrity of the building or any notable features, with the exception of any interior architecture that would influence the character of the building as perceived from the exterior.
Fifth Floor - This is a Renovation Zone. Similar to floors 3 and 4, this floor was remodeled and reconfigured in 1995 as private office space for a single government tenant. There are private offices around the entire perimeter, and open office cubicles in the corridors. There is no public access to this floor. The overall rectilinear plan relates to the original intent, but the finishes have been substantially modified. A new staircase inserted at the center of the west elevation connects floors 3, 4, and 5. This is not a historic feature, and is not sympathetic to the original architecture. Future changes on this floor would not have a discernable impact on the integrity of the building or any notable features, with the exception of any interior architecture that would influence the character of the building as perceived from the exterior.
Sixth Floor - This floor is a Renovation Zone. Designated as open space on the original plans, this floor has been remodeled and reconfigured over time to accommodate small offices and Bankruptcy Court hearing rooms. The design and materiality of these hearing rooms is a departure from the interior architecture of the Miles courtrooms. The corridor configuration remains original, although materials have been modified and replaced over time. Future changes on this floor would not have a discernable impact on the integrity of the building or any notable features.
Seventh Floor- This floor is a Renovation Zone. Designated as open space on the original plans, this floor has been remodeled and reconfigured over time for offices and Bankruptcy Court hearing rooms. The design and materiality for these hearing rooms is a departure from the interior architecture of the Mies courtrooms. The corridor configuration remains original. Future changes on this floor would not have a discernable impact on the integrity of the building or any notable features.
Eighth Floor - This floor is a Renovation Zone. This floor was originally designated as open space, and has remained primarily open floor plan, with the exception of the addition of a few walled offices, situated primarily at the perimeter corners. The elevator corridors have not been altered on this floor, and remain largely in original condition. Future changes on this floor would not have a discernable impact on the integrity of the building or any notable features.
Ninth Floor - This floor is a Renovation Zone. This floor has been heavily modified, and original materials are not evident. This floor has been demised into various configurations, including small offices and open office departments. The elevator corridor on the south end of this floor is in original condition. Ceiling and lighting conditions have been modified from the original building standard. Future changes on this floor would not have a discernable impact on the integrity of the building or any notable features.
Tenth Floor - This floor is a Renovation Zone. It was originally designated as open space, and has remained primarily an open plan, with the exception of some minor additions including walled offices at the perimeter corners. The elevator corridors have not been altered on this floor, and remain largely in original condition. Future changes on this floor would not have a discernable impact on the integrity of the building or any notable features.
Eleventh Floor - This floor is a Renovation Zone. This floor has been heavily modified, and original materials are not evident. Original plans indicated open office space for this floor. Similar too many of the lower floors in this building, original open floor plates were planned for development over time. This floor has been built out to include walled office spaces and demised open office departments. Future changes on this floor would not have a discernable impact on the integrity of the building or any notable features.
Twelfth Floor - Original plans for this floor specified the typical open office plan with structural provisions for the insertion of additional courtroom spaces over time. Four new courtrooms were added to this floor (and into the space above) in 1998. This courtroom expansion resulted in a floor plan configuration similar to other courtroom floors on upper levels, with a wide public corridor on the west side of the core with small lobby spaces and a narrow corridor on the east side of the core supporting private offices. This relationship to the original plan makes this space a Rehabilitation Zone, despite its 1998 origins. Conversely, the courtroom architecture from the 1998 expansion is a marked departure from the original Mies design precedents, therefore, this floor is largely designated as a Renovation Zone. Future changes on this floor would not have a discernable impact on the integrity of the building or any notable features.
Thirteenth Floor - This floor has been modified to accommodate the upper volume of the new courtrooms added to the twelfth floor. Hearing rooms and support spaces lining the perimeter wall are not designed with the historic courtroom palette. Additionally, public circulation and lobby spaces are unique to this floor and not a response to the precedent for public circulation on other historic courtroom floors. This floor is designated a Renovation Zone. Future changes on this floor would not have a discernable impact on the integrity of the building or any notable features.
Fourteenth Floor - Similar to floor twelve, this floor has been structurally and architecturally modified to accommodate courtroom expansion and associated support spaces. These courtrooms contain the "second generation" court rooms, designed by Dirk Lohan, and closely follow the design precedents of the Mies courtrooms. Public circulation on this floor was designed to match other historic courtroom floors. These areas are designated as a Restoration Zone. Other areas of the floor plan include Judges Chambers and support spaces that are not original features and are not designed based on the original building standards. For this reason, the balance of the floor is designated as a Renovation Zone. Future changes on this portion of the floor would not have a discernable impact on the integrity of the building or any notable features.
Fifteenth Floor - This floor is entirely private office space and has been modified over time from the original space plan, It is designated a Renovation Zone. Future changes on this floor would not have a discernable impact on the integrity of the building or any notable features.
Sixteenth Floor - This floor is a Renovation Zone. It has been modified from the original plans, or may not have been built out as intended. Original plans indicated hearing rooms and support spaces in a different configuration. Future changes on this floor would not have a discernable impact on the integrity of the building or any notable features.
Seventeenth Floor - Most of this floor is a Restoration Zone. This is a predominantly intact and original Mies courtroom floor, where there are also several Judges Chambers that remain in original condition. The layout and planning on this floor is intact, including the public corridors and sky lobbies. Any minor changes to the interior architecture on this floor are reversible. The balance of the floor, along the west wall, is deemed a Rehabilitation Zone, where future changes should be encouraged to be in keeping with the Miesian character to avoid intrusive modifications. Secondary support spaces have minor changes in finishes. Restrooms have been modified slightly to accommodate ADA accessibility, but have not been significantly modified.
Eighteenth Floor - This floor is designated a Restoration Zone. This floor includes the upper volume of the courtrooms on floor seventeen. The perimeter spaces contain Judges Chambers and smaller courtrooms, all still Miesian in character. The smaller hearing rooms around the perimeter have walnut paneling and are intact from the Mies era, inclusive of some of the furnishings. A portion of this floor is designated as a Rehabilitation Zone, since the hearing rooms along the west perimeter have been significantly altered over time. Restrooms on this floor have been modified for ADA accommodation.
Nineteenth Floor - This floor is also a combination of Restoration and Rehabilitation Zones. The central courtrooms on this floor are intact and original, as well as the judge's chambers on the east perimeter. Chambers and hearing rooms on the north and south perimeter have been modified.
Twentieth Floor - This is a Rehabilitation Zone. This floor is in nearly original condition relative to ceiling design and open floor plan design. Interior core elements such as door frames and finishes are intact and representative of the original building standard. Although modest in appearance, this floor is demonstrative of the open plan and level of finishes typical of many of the original open floor plans in the building. Future changes in use on this floor would ideally maintain the open plan.
Twenty First Floor - This floor is also a combination of Restoration and Rehabilitation Zones. The courtrooms and judge's chambers on the east wall on this floor are intact and original. Judges Chambers and hearing rooms on the north and south perimeter have been modified. The original circulation and public spaces remain.
Twenty Second Floor - This is a Restoration Zone. This floor surrounds the upper volumes of the courtrooms on the floor below. Perimeter hearing rooms and judges chambers are original including most of the Mies-designed courtroom furnishings and finishes. Due to the configuration of the smaller courtrooms and hearing rooms on this floor rather than the typical support spaces and office functions on other partial floors, the public corridor and lobby spaces differ from the typical design. Materials are largely original. Most of this floor is designated as a Restoration Zone due to its integrity of materials and plan, and it may have the highest number of original smaller court rooms.
Twenty Third Floor - This is a Restoration Zone. This is one of the most intact and well-preserved floors in the building, and is designated as a Restoration Zone due to its integrity from the Mies era. The majority of the plan, office spaces, and courtrooms are intact, the walls are still painted plaster, and the ceiling treatment is original. The only modification is the new granite sheathing applied in the elevator lobbies, which is a reversible condition.
Twenty Fourth Floor - This floor is occupied by the U.S. Marshall's office. The east half of this floor was designed specifically to accommodate the prisoner holding function. Original holding cells exist along the east wall adjacent to a corridor that is fully enclosed with steel mash screening. This floor is defined as a Rehabilitation Zone, due to that fact that the prisoner cells are a secondary utilitarian function, and there is a high likelihood that these cells no longer meet modern standards for security. The holding cells fall within the support space category, where accurate restoration would not be required. Nonetheless, the holding cells are an important indicator of the historic function of the building. They deserve documentation if prisoner holding requirements or other security demands require alterations to occur.
Twenty Fifth Floor - Areas within this floor are designated as Restoration Zone or Rehabilitation Zone. This floor features a central Ceremonial Courtroom with two standard courtrooms at the north and south cores, all of original Mies design. Judge's chambers and support spaces along the east perimeter wall are also original. The Ceremonial Court Room occupies two of the internal structural modules, making the room double the width of all the other courtrooms in the building. Designed as a flexible and universal courtroom, the various seals of the court are designed to slide in and out of wall pockets, depending on the magistrate and court applicable to each proceeding. Public circulation and lobby spaces are consistent with other courtroom floors and are in original condition, with the noted exception of walnut wall paneling added in 2003 in an effort to formalize the public realm of this floor and make it appear more appropriate for judicial functions. This change is sympathetic to the materials and detailing typical of the courtrooms, and is not overly intrusive to the character of the floor, largely due to the compatibility of the materials and conformance to the design motifs found in the court rooms.
Twenty Sixth Floor - This is one of the most intact and well-preserved floors in the building, and is designated as a Restoration Zone due to its integrity from the Mies era. The majority of the plan, office spaces, and courtrooms are intact, the walls remain painted plaster, and the ceiling treatment is original. Elevator lobbies remain in original condition. In this context, the public spaces are more important than the private spaces and internal office spaces.
Twenty Seventh Floor - This is one of the most intact and well-preserved floors in the building, and is designated as a Restoration Zone due to its integrity from the Mies era. The majority of the plan, office spaces, and courtrooms are intact, the walls are still painted plaster, and the ceiling treatment is original. The only modification is the elevator lobbies.
Twenty Eighth Floor - This floor is designated as a Renovation Zone, due to its use as building support and mechanical systems. There is no architectural/historical reason that this floor and the related equipment could not be altered or upgraded as needed if the mechanical systems were modified.
Twenty Ninth Floor - This floor is designated as a Renovation Zone, due to its use for building support and mechanical systems. This floor contains air handling units and exhaust fans. There are large central station air handler units that service the building core areas, and dedicated systems for court suites. Water-cooled air conditioning units serve some dedicated tenant spaces such as computer rooms. There is no architectural/historical reason that this floor and the related equipment could not be altered or upgraded as needed if the mechanical systems were modified.
Thirtieth Floor - This floor is designated as a Renovation Zone, due to its use as building support and mechanical systems. There is no architectural/historical reason that this floor and the related equipment could not be altered or upgraded as needed if the mechanical systems were modified. The space is essentially utilitarian, unfinished space.
Original materials and finishes should remain in place in all locations, and not be concealed or obscured by rehabilitation measures.
Alterations that impact the perimeter window walls - interior or exterior - must be reviewed for impact and alterations.
In the Ground Floor lobby, installation of security stations and surveillance monitors should be carefully evaluated to avoid further intrusive encroachment or any loss of historic materials.
The corridor configuration throughout the building should not be altered or breached. This is the basis of the floor plan, and should remain a discernable feature of the building.