The Bessemer & Lake Erie Railroad Bridge it is a truss bridge

Truss bridge

A truss bridge is a bridge composed of connected elements which may be stressed from tension, compression, or sometimes both in response to dynamic loads. Truss bridges are one of the oldest types of modern bridges...

 that carries the Canadian National Railway

Canadian National Railway

The Canadian National Railway Company is a Canadian Class I railway headquartered in Montreal, Quebec. CN's slogan is "North America's Railroad"....

's Bessemer and Lake Erie Railroad

Bessemer and Lake Erie Railroad

The Bessemer and Lake Erie Railroad is a class II railroad that operates in northwestern Pennsylvania and northeastern Ohio.The railroad's main route runs from the Lake Erie port of Conneaut, Ohio to the Pittsburgh suburb of Penn Hills, Pennsylvania, a distance of 139 miles...

 division across the Allegheny River

Allegheny River

The Allegheny River is a principal tributary of the Ohio River; it is located in the Eastern United States. The Allegheny River joins with the Monongahela River to form the Ohio River at the "Point" of Point State Park in Downtown Pittsburgh, Pennsylvania...

 between the Pittsburgh suburbs of Plum

Plum, Pennsylvania

Plum is a borough in Allegheny County, Pennsylvania, United States. The population was 27,126 at the 2010 census.Plum is often referred to as "Plum Boro" or more correctly "Plum Borough" by locals to distinguish it from its previous status as a township...

 and Harmar Township, Pennsylvania. In 1897, a low-level bridge was built on this site; in 1918, the original piers were doubled in height and the current high-level, double-tracked structure was put into place.