The Hot Metal Bridge is a truss bridge in Pittsburgh, Pennsylvania that crosses the Monongahela River. The bridge consists of two parallel spans on a single set of piers: the former Monongahela Connecting Railroad Bridge, built in 1887, on the upstream side and the former Hot Metal Bridge, built in 1900, on the downstream side. The Monongahela Connecting Railroad Bridge carried conventional railroad traffic, while the Hot Metal Bridge connected parts of the J&L Steel mill, carrying crucibles of molten iron from the blast furnaces in Ladle transfer cars to the open hearth furnaces on the opposite bank to be converted to steel. During World War II 15% of America's steel making capacity crossed over the Hot Metal Bridge, up to 180 tons per hour. The upstream span was converted to road use aft