Conduit Road
The United States Army Corps of Engineers built the Washington Aqueduct between 1853 and 1864, to supply water from Great Falls to Washington. The aqueduct was covered in 1875, and it became known as Conduit Road. The Union Arch Bridge, which carries the aqueduct across Cabin John Creek, was the longest single-arch bridge in the world at the time it was completed in 1864. The road is now named MacArthur Boulevard.