When railroads replaced steamboats, Fort Benton's importance as a trade center declined. In response, Fort Benton businessmen formed the Benton Bridge Company to construct a bridge across the Missouri River to capture the trade of the rapidly developing Judith Basin. The first steel bridge across the Missouri River in Montana made it possible for ranchers and farmers to ship their livestock and grain from the Fort Benton railhead. It thus preserved Fort Benton's significance to regional trade. Since the Missouri was classified as a navigable waterway, the newly formed Benton Bridge Company needed federal permission to build. Congress approved the project after requiring that one span be built on a pivot so the bridge could open to let boats through. In 1888, the firm of Haney and Ryann began sinking the bridge's piers, which they protected with ice breaks built of heavy timbers. The work was dangerous; two men died during construction. The Milwaukee Bridge and Iron Works Company built the steel and iron superstructure. On completion, the newspaper declared the 825-foot, six span, pin-connected, through-truss bridge "as strong and durable as its is handsome." It cost pedestrians 5 cents and a horse and buggy 25 cents to cross. Each head of cattle cost 12.5 cents, with special rates of large droves. The county purchased the structure in
1892. After June 1908 floods washed out the swing span, the Army Corps of Engineers gave permission to replace it with a permanent pin-connected, steel Parker through-truss span. Vehicles continued to cross the Missouri over "the Great Iron Bridge" until 1962.