Marquette, Iowa became a major hub on the Chicago, Milwaukee and St. Paul Railway, as grain from throughout Iowa and Minnesota was sent through the city en route to Lake Michigan. Initially trains had to be ferried across the river between Marquette and Prairie du Chien, Wisconsin in order to continue their journey. A better solution was found by two men named Michael Spettel and John Lawler, who designed a permanent pontoon bridge to span the river in 1874. Prairie du Chien businessman Lawler took most of the credit for this invention, and made a small fortune through its operation. Marquette subsequently became home to a major rail yard, which even as late as 1920 was the busiest in Iowa, employing 400 people.
However, the railroad's significance declined and the last passenger train stopped in Marquette in 1960. The pontoon bridge was disassembled in 1961.