The existing Pratt truss structure of the Sulfite Bridge was replaced with a framed trestle bridge erected at this Franklin
site in 1891 or 1892 built by the Franklin and Tilton Railroad. The bridge is located one-half mile east of Franklin Falls and south of U.S. Route 3 over the Winnipesaukee River, in Merrimack County
This unusual bridge, called the Upside Down Covered Bridge because the railroad track crosses over the top of the structure rather than running through its center, was built by the Bridge and Building Department of the Boston and Maine Railroad in 1896, and appears to be the only deck-covered railroad bridge left in the United States. The bridge bears its name due to the large amounts of sulfur transported over the rail lines for use by the giant pulp and paper mills not far from the bridge.
Service over the line was suspended in 1973 and what was believed to be an arson fire, burned the inside of the bridge in 1980.
The Sulphite Bridge is listed on the National Register of Historic Places.