Keokuk Rail Bridge
The Keokuk & Hamilton Bridge is one of three remaining in Iowa that were designed by Ralph Modjeski, one of this country's premier early 20th century bridge engineers. The eleven-span, double-deck steel superstructure was built in 1915-1916 on piers retained from an earlier (1869-1871) structure, to meet greater loading requirements from railroads that operated across the Mississippi at this point.
The Keokuk & Hamilton Bridge Company was incorporated in 1868 to further railroad and commercial development in Keokuk and in Hancock County, Illinois. The firm's president until 1914 was Andrew Carnegie, who had interest in the railroad participating in the venture. The first Keokuk & Hamilton Bridge was built by Carnegie's Keystone Bridge Co. from designs by Thomas Curtis Clarke, later a founder of Clarke, Reeves & Co. (which is best known under its subsequent name, Phoenix Bridge Co.). This structure stood until 1915, when pressure from Keokuk businessmen and the threatened erection of a competing bridge forced the Keokuk & Hamilton Bridge Co. to reconstruct its span.
The replacement structure remained in corporate ownership until January 1949, when it was turned over to the city of Keokuk. Although the city intended that there should be no tolls for vehicular traffic, the span remained "free" for only three years. Tolls were reimposed in 1952, in order to finance maintenance and also major repairs to the piers, which were rejacketed with reinforced concrete in 1951-1952.
I walked on the observation deck of this bridge in June of 2011. I highly doubt that it is used that much because there was grass covering the rails, and I have seen few photos since the new bridge opened of the old bridge in the closed position. Maybe they could open the other side to pedestrians...
The vehicle portion of it is quite interesting, you could see through it, I do not know why they don't do this type of bridge more often, as if the road is not very well traveled it would be very efficient.