The 1174 foot long truss bridge in Pittsburgh, Pennsylvania crosses the Monongahela River and consists of two parallel spans on a single set of piers. The Monongahela Connecting Railroad Bridge (MRC Bridge), built in 1887, and the Hot Metal Bridge, built in 1900, are separate spans but often go by one name: the Hot Metal Bridge.
The MCR Bridge had two railroad tracks and carried railroad traffic for the Monongahela Connecting Railroad. The Hot Metal Bridge connected parts of the Jones & Laughlin Steel Mill, carrying molten steel from the blast furnaces to the rolling mills on the opposite bank of the river. The floor of the bridge was lined with metal plates to protect the wooden railroad ties and river traffic beneath the bridge from molten metal sparks that spewed from the opening on the tops of the cars. During World War II an average of 180 tons of molten steel passed over the bridge ever hour; fifteen percent of American steel capacity at the time.