After the fur trade declined in the mid-nineteenth century, Prairie du Chien's attention shifted to agriculture and the railroad. Although the city was first connected to the Milwaukee & Mississippi Railroad in 1857, the width of the Mississippi River posed a challenge for further expansion of the railroad into Iowa. This problem was temporarily solved by disassembling the trains at Prairie du Chien and ferrying them across the river to be put back on the tracks on the other side. A better solution was found by Michael Spettel and John Lawler, who designed the permanent Pile-Pontoon Railroad Bridge to span the river in 1874. Lawler took most of the credit for this invention, and made a small fortune through its operation. The bridge remained in use until its removal in 1961.