The 15th Street Historic District is a threeblock area based upon the Treasury Department building and inspired by the City Beautiful movement. By the early twentieth century, the former residential area had yielded to commercial buildings, especially the banks on 15th Street designed in the Beaux-Arts Classical style. Those on the north side of Pennsylvania Avenue facing the Treasury Building were especially important. As financial institutions clustered together and supporting office structures filled in the interstices, the area took on the character of a financial district.

Among the area's anchors are the large red brick National Savings and Trust Company (
DE35.1), designed by James Windrim in 1888, located at the northeast corner of New York Avenue and 15th Street. Two classical-styled bank buildings at the northwest corner of 15th Street and Pennsylvania Avenue, the Riggs National Bank (
DE35.2) and the American Security and Trust Company (
DE35.3), were designed by York and Sawyer. The Union Trust Building (
DE35.4) with its Corinthian columns at 1500 H Street NW was a work of Wood, Donn and Deming. Daniel Burnham's firm designed the Southern Building (
DE35.5) at 1425 H Street in 1910, a triumphant Beaux-Arts office building bearing some of the district's most elaborate terracotta detail. The Woodward Building (
DE35.6) at 1426 H Street, designed by the Washington firm of Harding and Upman in 1911, is another example using terracotta on brick. In their common function, bulk, cornice line, and vintage, these buildings represent the private sector's response to the extension of the McMillan Plan's Executive Group that surrounded the White House.