The St. Louis Bridge over the Mississippi River was
designed by James Buchanan Eads, who built iron-clad steamers during the
Civil War for the Federal Government, but who had never before designed a
bridge. He chose an arch design, with the arches made of cast steel tubes.
It was the first use of cast steel in a major bridge. The bridge was begun
in 1867 and opened for traffic in 1874.
The arches were erected from each pier or abutment and
supported by cantilevers until they could be joined at the center. The
process of closure was a tricky one, as all eight tubes had to join
precisely and simultaneously. This view from the American periodical
Scientific American shows the closing of the east arch, which was
successfully accomplished in September, 1873.