National Archives Building

This massive structure was constructed above an underground stream. 8,575 piles had to be driven into the unstable soil, before pouring a huge concrete bowl as a foundation. Another difficulty arose over the choice of building materials. Both limestone and granite were authorized as acceptable, but construction began during the darkest days of the Great Depression, and suppliers of each material lobbied fiercely to have the government use their stone. Ultimately, as in the other Federal Triangle buildings, limestone was used for the exterior superstructure and granite for the base.