The Bessemer & Lake Erie Railroad Bridge is a truss bridge that carries the Canadian National Railway's Bessemer and Lake Erie Railroad division across the Allegheny River between the Pittsburgh suburbs of Plum and Harmar Township, Pennsylvania. In 1897, a single track trestle and viaduct was built on this site; in 1918, the original piers were doubled in width, the current double-tracked structure built alongside, and then slid into place.

(Source: Wikipedia)