The Patent Office Building was constructed wing by wing on two city blocks over the 32-year period beginning in 1836. The spacious top-floor halls were designed for the display of patent models in cases almost nine feet high. Architect Robert Mills, who also designed the Washington Monument, supervised the construction from 1836 to 1851. He was followed by architect Thomas U. Walter, designer of the dome of the United States Capitol.
When completed in 1868, the Patent Office was the largest office building in the United States, occupying 333,000 square feet and constructed at a cost of $2,347,000. By 1870 the third-floor galleries displayed 200,000 patent models and formed a continuous interlocking exhibition space one-quarter mile in circumference. As many as 100,000 visitors a year came to view the patent models and historic curiosities on display in the building.
East Model Hall, 1856 (woodcut):
From 1852 to 1917, the US Department of Interior occupied much of the lower two floors of the building. The Patent Office moved out in 1932, and the US Civil Service Commission took possession for the next 31 years, during which time the building suffered from alterations and lack of maintenance. After being saved from demolition for a parking garage, the structure was transferred to the Smithsonian Institution and was renovated for the National Portrait Gallery and the Smithsonian American Art Museum, which opened in 1968.
The Patent Office Building in 1965 was designated a National Historic Landmark, the highest honor an historic structure can receive. In 1966 it was listed on the National Register of Historic Places.
South Portico, 1850:
The Patent Office Building is one of the finest examples of Greek revival architecture in the country, with porticoes modeled after the Parthenon in Athens. This 1850 photograph shows the original stairs leading to the second-floor portico with its massive Doric columns. In 1936 the steps were removed from the widening of F Street, and the current entrance at ground level was created. When funding becomes available, the stairs will be reconstructed, although in a different configuration.
The columns in the photograph are draped in black in mourning for the death of President Zachary Taylor. The room in which you are standing is under the right side of the portico.