Potomac Annex 2 (Old Naval Observatory), Washington, DC

The old United States Naval Observatory has undergone many alterations and additions since its initial 1844 configuration. The original 1844 Observatory was a 2-story brick structure with radiating wings to the east, west and to the south. Later significant additions include the 1847 Superintendent's Residence to the east; the 1897 lecture hall (which replaced the 1869 Transit Circle Room) the 1895 south rotunda (built on the foundations of the 1873 Great Equatorial Telescope Rotunda); the second-story additions (1902, 1903) to the original one-story wings; and the two 20th century stucco additions to the south. The original 1844 section of Building 2 is a two-story plus basement brick structure, ornamented by a wood cornice and surmounted by a observation dome. The building faces north and is square in plan with radiating wings to the east, west and south. its overall appearance is of a solid classical structure with Greek Revival overtones. The main block of this section is basically a symmetrical cube five window bays wide by two high; the door is the central feature on the north facade. Brick pilasters divide the central bay from the two flanking bays and terminate the ends of the main block. The entrance is centered on the facade and is fitted with a wood and glass door with glass transom and sidelights. The entry stoop is composed of a short flight of granite steps with iron railings on either side. The windows are typically 6/6 single hung wood units. The masonry openings are distinguished by decorative hoods with acanthus leaf brackets supporting wood lintels. The dome which is centered on the building's main block is 23 feet in diameter and rests on a 7 foot circular wall drum. One-story wings originally radiated to the south, east and west from the central core and were extended during the 19th century. The exterior of the wings was changed substantially in 1902-1903 when the second story additions were constructed and apertures and entrances were bricked-in. The brick Superintendent's Residence was built directly to the east of the Observatory in 1847. It is a two-story structure raised above a basement and is three window bays wide. A two-story back building abuts the south facade. The center bay of the north facade is flanked by and the corners terminated by, brick pilasters similar to those on the Observatory. The main entry is centered on the facade and is served by a red sandstone stoop with a short flight of steps and finished with a decorative iron railing. The door is wood and glass surmounted by a glazed transom and flanked by sidelights. The windows are typically 6/6 single hung units set within simple enframments with sandstone lintels and sills. Pintels from original louvered blinds are still extant on the exterior. As with the main block of the Observatory, are ways lie at the base of the north and south facades of the residence. For the first year of its existence the house stood as a detached structure. A year later, in 1848, the east wing of the observatory was extended by two bays to connect the Residence to the Observatory. Ghosts in the brockwork on the south elevation indicate that there were porches on the east and west sides of the south elevation with access to the southeast and southwest rooms by doors, which were later converted to windows. Extending to the south from the 1844 Observatory is the 1873 south wing extension. The addition was built in two phases and includes a T-shaped section and a rotunda. The T-shaped extension was raised to a two-story adjoining elevation bridges the gap between the rotunda and the T-section. The rotunda was taken down and built ca. 1896; the existing structure is a brick drum set on a stone foundation. The metal roof to the Rotunda is conical and capped with a glazed cupola. A free standing corbelled brick chimney lies to the northeast of the rotunda. An addition was constructed to the west of the Observatory in 1896, undergoing a major renovation in 1895 when the transit house was taken down. The new structure was built on the old foundation. It is a brick structure characterized by large arched window openings reflecting the double-height of the space within. The windows are 2/2 singe hung wood units. Brick pilasters, similar to those on the Observatory, flank the sides of the addition. An entrance in centered on the north elevation; it is characterized by a semi-octagonal projecting vestibule with a parapet wall. A sheet metal cornice surmounts the masonry walls. Two further additions were constructed in 1917-1918 as part of a Naval Medical School and Hospital expansion. Both are two-story structures rising above a basement level. The walls are clad with stucco and are surmounted by a wood cornice. The foundation walls are poured concrete. A Colonial Revival entrance is located on the south elevation of the east stucco addition and is served by a set of granite steps. Additional entrances are located at the basement level of both east and west stucco additions. The windows are typically 6/6 single hung wood units. The exterior appearance of Building 2 is retained from the 1918 period.

The old United States Naval Observatory, currently known as Building 2 Potomac Annex, is listed on the National Register of Historic Places (1966) and is a National Historic Landmark.

The Naval Observatory operated on Observatory Hill from 1844 to 1893 and was a symbol of success in America's early struggle for intellectual, scientific and technological independence from Europe. As an institution, it represented the young nation's aspirations to take its place in the world scientific community. It also allowed America to generate its own astronomical data without reliance on Europe; an important step in developing independence in navigation and whaling, two endeavors critical to the commercial success of the courtly in the nineteenth century. Instituting a national observatory enjoyed the support and sustained the attention of American's leaders from the beginning, including Presidents Thomas Jefferson and John Quincy Adams.

Significant discoveries, functions and events associated with the National Observatory include both navigational as well as astronomical pursuits. The Observatory was responsible for cataloging locations of stars and planets. It was also designed to rate maritime chronometers for accuracy. As telegraphic technology developed, the Observatory functioned as the nation's official time-keeper, standardizing the measurement of time throughout most of the country. Matthew Fontain Maury (Director from 1844-1861) made contributions to the fields of navigation and oceanography, particularly his publication of the "Abstract Log for the Use of American Navigators" (1848) and "The Physical Geography of the Sea" (1855).

Its middle history, between the years 1893 and 1942, allowed "Observatory Hill" and its anchor building to mature into new uses with new occupants including the Naval Museum of Hygience and, later, the Naval Medical School and Hospital. These later developments enhance the significance of the site, both through the quality of architecture and through the important role the School and Hospital played as the Navy's medical headquarters in the Nation's Capital. Potomac Annex currently functions as administrative offices for the Naval Bureau of Medicine and Surgery and serves as headquarters of the Surgeon General of the Navy.

Although changed by many alterations and additions, much of the original structure exists as the central core of the building. The late-Greek Revisal style of the original building core reflects the architectural taste of the the 1840s when the building was constructed. It was an appropriate institutional style and symbolized the democratic aspirations of the young country. Though there was no formally trained architect for the building, great care was given to the building's final form. In 1838, Lieutenant James Melville Gillis was promoted to director of the Deport of Charts and Instruments. As Director, Lieutenant James Mellvlle Gillis was responsible for overseeing the construction of the Observatory. With no formal astronomical training, he sought the advice of director of the leading observatories of the day, including observatories in London, Oxford, Cambridge, Dublin, Hamburg, Berlin, Leipzig, and Munich. His search provided him with a plan that incorporated the most appropriate dimensions suitable for the instruments of a working observatory. Gillis hired an English draftman to draw plans according to his specifications.

The Observatory's Greek Revival Style was reflected, and sometimes simply replicated, in detail as new additions were made to the building. The quality of the design and construction, as well as the unusual technological requirements of the ordinal observatory building, render it a significant contribution to American architecture. The attention and respect paid to the original design intent during subsequent construction makes the whole a comprehensive and pleasing architectural composition.

Specific Significance Years: 1843, 1893
Area of Significance: Military science

Description Architect
1843 1847 Original Construction Gilliss, James Melville
Last Reviewed: 2017-09-21