Pile–Pontoon Railroad Bridge

A permanent bridge between Marquette and Prairie du Chien, Wisconsin was thought impractical, in part due to substantial river traffic which would have required clear spans high above the water.

In the late 1860s, the Milwaukee Road's agent John Lawler conceived a ferry crossing, using barges with rail tracks on their decks.

A better solution was found by Michael Spettel and Lawler, who patented a permanent pontoon bridge system to span the river in 1874.

At each end, a short, ramped length of steel span was provided, carrying the track onto the adjoining trestles.

Prairie du Chien businessman Lawler took most of the credit for this invention, and made a small fortune through its operation.