The Federal Triangle was conceived as part of the Senate Park Commission Plan of 1901, commonly referred to as the McMillan Plan, after Senator James McMillan of Michigan. The McMillan Plan sought to re-establish the original intent of the L'Enfant Plan and improve the central corridor of Washington that had not developed as intended and did not reflect a positive image for the new republic.
During the Civil War the area, which is now the Federal Triangle, had become a notorious neighborhood where General Joseph Hooker's troops, then encamped outside the city protecting the approaches from rebel attack, would gravitate at night. Already designated "Murder Bay" by Washingtonians, the neighborhood was now also known as "Hooker's Brigade" and was a rabbit warren of bars and bawdy houses.
After World War I, the need for new and expanded government office buildings became critical by the Hoover Administration. In 1926, the Public Buildings Act was passed by Congress launching the most ambitious federal construction in Washington's history. Secretary of the Treasury Andrew Mellon was given broad authority to "provide suitable accommodation" for federal executive departments in the City of the District of Columbia. Secretary Mellon appointed a Board of Architectural Consultants to study proposals and make recommendations for the development and design of the buildings within the Federal Triangle.
The project was completed in three phases. The first phase of the project, including the Commerce and IRS buildings, was completed when the country found itself on the brink of the Great Depression. Subsequent phases were funded throughout the Great Depression until resources again were diverted on the brink of World War II. The Triangle was not completed until 1997 when the Reagan building occupied the final site.