The Hennepin Canal is a manmade waterway built to carry cargo barges between the Illinois and Mississippi Rivers, cutting more than 400 miles from the river route between Chicago and Rock Island and linking with the Rock River for eight miles between Green Rock and Milan. An engineering marvel, it helped pioneer techniques and materials later used widely in construction, including becoming the first American canal built with concrete instead of cut stone, a revolutionary approach later copied by engineers around the world and reflected in the design of the Panama Canal. Although planning began in 1854, the canal did not open until 1908, after railroads had already taken much of the freight trade, and its fortunes declined further when the Illinois River was enlarged in the 1920s to handle bigger barges that could not fit through the canal. Built over 17 years by thousands of men using methods that included horse-driven earth scrapers and barge machines, the canal reached its peak in 1929, carrying 30,161 tons of cargo, only 1/600th of its estimated capacity. It never achieved real commercial success and was closed to all traffic in 1951, but it remained a popular recreational destination for boating, canoeing, fishing, biking, hiking, and picnicking. A lift bridge on the Illinois and Mississippi Hennepin Canal, erected in 1904 to give farmers access to their land, was raised by turning a central wheel windlass that lowered large weights and lifted the bridge by chains so canal boats could pass.