Bollman Truss Railroad Bridge
The Bollman Truss Railroad Bridge across the Little Patuxent River at Savage, Maryland, is one of the oldest standing iron railroad bridges in the United States and the sole surviving example of a revolutionary design in the history of American bridge engineering. The 160-foot (48.8 m) double-span was built in 1852 at an unknown location on the main line of the Baltimore and Ohio Railroad.
Source: Wikipedia — Bollman Truss Railroad Bridge (CC BY-SA 4.0)