Washington Monument foundation, 1879

The cornerstone of Robert Mills's most famous structure, the Washington Monument on the National Mall, was laid on the Fourth of July, 1848.  Work stopped on the immense obelisk in 1854 and did not resume for over thirty years due to funding and engineering problems, and the severe disruptions of the Civil War.  Before work resumed, the Army Corps of Engineers, which had replaced the private construction firm, reinforced the foundation with the huge concrete slabs seen here.  In an interesting juxtaposition, the wide portico of Mills's Treasury Building is faintly visible at upper left.

Foundation of the Washington Monument, 1879