Bollman suspension truss bridge #3
According to Wikipedia - "The Bollman Truss Railroad Bridge at Savage, Maryland is the sole surviving example of a revolutionary design in the history of American bridge engineering. The 160 foot (48.8 m) double-span truss bridge is one of the oldest standing iron railroad bridges in the United States. It was the first successful all-metal bridge design to be adopted and consistently used on a railroad. The type was named for its inventor, Wendel Bollman, a self-educated Baltimore engineer.
The bridge was built for an unknown location on the main line of the Baltimore and Ohio Railroad in 1852, and was moved to its present location, spanning the Little Patuxent River on the spur to the Savage Mill, in 1887. "