Occupying an entire city block, the Old Post Office is located on the north side of the Federal Triangle along Pennsylvania Avenue, the link between the Capitol and the White House. Designed by Willoughby J. Edbrooke, Supervising Architect of the U.S. Treasury Department, the Old Post Office exhibits a matured version of the Romanesque Revival style, which was popularized by renowned architect H.H. Richardson in the late nineteenth century. The building’s massive scale, rustication, arched fenestration, and ornamentation evokes the Romanesque Revival style, while incorporating a variety of complementary features such as Byzantine sculptural capitals, French Gothic dormers and sculpture, and French Renaissance detailing. The eclectic effect of these details creates a delightful visual vitality that is now regarded as a virtue along Pennsylvania Avenue’s predominantly Classical Revival corridor.
Sheathed in granite from Vinalhaven, Maine and set upon an iron and steel superstructure, the vast nine-story building was the first steel-frame building erected in Washington DC. Unlike other contemporary tall buildings, the five-feet-thick granite masonry walls are self-supporting, while steel girders support the interior floor beams. As a fire-proofing measure, a terracotta shell encases each steel and iron structural member.
Along Pennsylvania Avenue, three large semicircular Romanesque arches frame the principal entrance and are ornamented with Romanesque Revival columns, capitals, moldings and richly foliated spandrels. The rock-cut rustication at the first-story and mezzanine walls contrast with the smooth surfaces of the upper stories, where vertically stacked bays are crowned with a continuous springing course and wide arches at the fifth story. The sixth and seventh floors, separated from the lower floors by a stringcourse, are composed of narrow, two-story window units separated by twin-columned mullions, capped by arcades. At the top of the wall, a wide, dentiled cornice is reminiscent of the machicolation used in medieval fortifications.
The facade (north elevation) is divided into three vertical sections, defined by the central recessed portion of the building. At its center, a lofty clock tower projects forward and rises 315 feet to a hipped roof accentuated by pinnacles at the belfry. Tall stone pilasters support the clock face, which is simply framed by a Roman arch. Above this, an observation deck is pierced by three large, arched openings that offer some of the best views of the city. The east and west wings of the facade project forward slightly, with corners embellished by soaring pinnacles with conical roofs. The steeply pitched, slate-clad roof is pierced by stone-clad dormers adorned with stone finials.
The most remarkable feature inside is the nine-story light court topped by an enormous skylight that floods the interior with natural light. When it was built, the room was the largest, uninterrupted interior space in Washington. The building’s 1977 renovation uncovered the skylight and added a glass-enclosed elevator on the clock tower’s south side to provide visitor access to the observation deck.