Covered Wood Railroad Bridges Sulphite Covered Railroad Bridge, Franklin New Hampshire

Some of the earliest railroad bridges were timber structures because wood was abundant, cheap, and easy to work with. In 1830, Lewis Wernwag built the first wood railroad bridge in the United States for the Baltimore & Ohio Railroad over the Monocacy River in Maryland. Within a short time, wood bridges were commonplace on America's growing network of railroads.

Presumably, hundreds of covered railroad bridges were built in the nineteenth century. In 1841, one English traveler noted, "The timber bridges of America are justly celebrated for their magnitude and strength. By their means the railways of America have spread widely and extended rapidly." By the late nineteenth century, most railroad bridges were being built of iron or steel. In 1957, there were only twenty-nine surviving timber truss railroad bridges in the country. Today there are eight. The Sulphite Railroad Bridge is the only surviving deck truss covered bridge in the United States.