Digging into the archives for this one.
These columns were originally part of the Capitol Building in Washington DC. They were removed when the East Portico was rebuilt in the 1950's. They were relocated to a large field in the National Arboretum.
Makes one wonder if these were still in place our government would be in the shambles that it is. (sorry about the political tone) Do very much love the inclusion of the people, gives great sense of scale.