The Pile–Pontoon Railroad Bridge was a floating bridge which crossed the

Mississippi River The Mississippi River is the second-longest river and chief river of the second-largest drainage system in North America, second only to the Hudson Bay drainage system. From its traditional source of Lake Itasca in northern Minnesota, it f ...

in northern

Iowa Iowa () is a state in the Midwestern region of the United States, bordered by the Mississippi River to the east and the Missouri River and Big Sioux River to the west. It is bordered by six states: Wisconsin to the northeast, Illinois to the ...

. From 1857

Marquette, Iowa Marquette is a city in Clayton County, Iowa, United States. The population was 429 at the time of the 2020 census, up from 421 in 2000. The city, which is located on the Mississippi River, is named after Jesuit missionary Jacques Marquette, who ...

became a major hub on the Chicago, Milwaukee and St. Paul Railway, as grain from throughout

and

Minnesota Minnesota () is a state in the upper midwestern region of the United States. It is the 12th largest U.S. state in area and the 22nd most populous, with over 5.75 million residents. Minnesota is home to western prairies, now given over to ...

was sent through the city en route to

Lake Michigan Lake Michigan is one of the five Great Lakes of North America. It is the second-largest of the Great Lakes by volume () and the third-largest by surface area (), after Lake Superior and Lake Huron. To the east, its basin is conjoined with that o ...

. A permanent bridge between Marquette and

Prairie du Chien, Wisconsin Prairie du Chien () is a city in and the county seat of Crawford County, Wisconsin, United States. The population was 5,506 at the 2020 census. Its ZIP Code is 53821. Often referred to as Wisconsin's second oldest city, Prairie du Chien was esta ...

was thought impractical, in part due to substantial river traffic which would have required clear spans high above the water. Goods were initially transported by boat across the river, which required unloading and reloading of railroad cars. In the late 1860s, the Milwaukee Road's agent John Lawler conceived a

ferry A ferry is a ship, watercraft or amphibious vehicle used to carry passengers, and sometimes vehicles and cargo, across a body of water. A passenger ferry with many stops, such as in Venice, Italy, is sometimes called a water bus or water taxi ...

crossing, using barges with rail tracks on their decks. Because there are two channels separated by an island, each channel required a barge which was pulled across by cables, and a small

rail yard A rail yard, railway yard, railroad yard (US) or simply yard, is a series of tracks in a rail network for storing, sorting, or loading and unloading rail vehicles and locomotives. Yards have many tracks in parallel for keeping rolling stock or u ...

crossing the island connecting the two ferries. This allowed

transshipment Transshipment, trans-shipment or transhipment is the shipment of goods or containers to an intermediate destination, then to another destination. One possible reason for transshipment is to change the means of transport during the journey (e.g. ...

of railroad cars without unloading, but was still less than efficient. A better solution was found by Michael Spettel and Lawler, who patented a permanent

pontoon bridge A pontoon bridge (or ponton bridge), also known as a floating bridge, uses float (nautical), floats or shallow-draft (hull), draft boats to support a continuous deck for pedestrian and vehicle travel. The buoyancy of the supports limits the maxi ...

system to span the river in 1874. This comprised piled

trestles ATLAS-I (Air Force Weapons Lab Transmission-Line Aircraft Simulator), better known as Trestle, was a unique electromagnetic pulse (EMP) generation and testing apparatus built between 1972 and 1980 during the Cold War at Sandia National Labora ...

built out into the river, and two pontoons: A 210-foot unit on the east channel, and a 227-foot unit on the west. Each pontoon was hinged at one end to allow it to float open, and was pulled closed by a steam-powered cable. As well as allowing for river traffic, this allowed end-of-winter ice floes to pass down the river without risk of damaging the structure. The pontoons were built with a timber-framed deck which could be raised or lowered by as much as 18 feet to allow for changes in the river level, which can vary by as much as 22-1/2 feet (at extreme high water, the bridge could not be used). Adjusting and supporting the deck with timber blocks was a laborious process requiring much manual work. At each end, a short, ramped length of steel span was provided, carrying the track onto the adjoining trestles. Train speed across the pontoons was limited to 7 miles per hour. 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

, which even as late as 1920 was the busiest in Iowa, employing 400 people. The original crossing was upgraded with replacement of the eastern pontoon in 1914, and a longer (276-foot) western pontoon in 1916; the longest in the world at that time. The replacement spans included steam-powered lift machinery to adjust the height of the track deck.Hegeman, Jeannette: “The Bridge that Floats,” '' Trains and Travel'' magazine, January 1952 However, the railroad's significance declined and the last passenger train stopped in Marquette in 1960. The pontoon bridge was disassembled in 1961.

References

See also