This image presents an alternate view of the intersecting bridges over Cabin John Creek. The Union Arch Bridge (also known as the Cabin John Bridge) carrying both the Washington Aqueduct and MacArthur Boulevard, can be seen in the background. Constructed between 1857-1862, the Union Arch Bridge was the largest single-span masonry arch in the world until 1903.
While the main arch of the bridge is constructed in granite, nine supplementary internal arches are hidden within the sandstone sidewalls. These arches (five in the west spandrel and four in the east spandrel) distribute the weight of the aqueduct and of the road evenly over the main arch. Cabin John Parkway Bridge, described in detail in this post, appears on the left of the image.