The Last Bollman Bridge

What you're passing near right now is one of the quietest engineering landmarks in America. Spanning the Little Patuxent River at Savage, Maryland, the Bollman Truss Railroad Bridge is the only surviving example of a design that fundamentally changed how the United States built its railroads.

The man behind it was Wendel Bollman, and his story is almost as remarkable as his bridge. Bollman was self-educated, a carpenter by training, who started as a laborer for the Baltimore and Ohio Railroad in eighteen twenty-eight, helping lay the company's very first stretch of track. He worked his way up, apprenticed under chief engineer Benjamin Henry Latrobe the Second, and eventually devised a structural system that nobody in American engineering had tried before.

In eighteen fifty-two, Bollman patented a composite truss that put different materials to work doing different jobs. All the compression members, the top chord, the end posts, the verticals, were cast iron, which resists being crushed. All the tension members, the diagonals that actually pull and hold the structure together, were wrought iron, which resists being stretched and torn. It sounds straightforward today, but at the time it was a revelation. Before Bollman, most American railroad bridges were wood, which rotted, caught fire, and had to be constantly rebuilt.

More than one hundred Bollman truss bridges went up between eighteen fifty and eighteen seventy-five, nearly all of them on the Baltimore and Ohio line. They carried the locomotives and freight that knit the nation together during the most explosive era of railroad expansion in American history.

All but one are gone. This one, a double span one hundred sixty feet across, was built in eighteen fifty-two and moved to its current location at Savage thirty-five years later. It was recognized in nineteen sixty-six as the very first National Historic Civil Engineering Landmark designated by the American Society of Civil Engineers. Restored in nineteen sixty-eight, it now stands in the Historic Savage Mill Marketplace, a monument to the self-taught carpenter who changed American infrastructure.

When you drive past a steel bridge today, you're looking at a world Bollman helped invent.