Historic canal network connecting Lake Michigan with the Mississippi River, a distance of 526 km/327 mi. Construction of this important transportation artery in the 19th century ensured that the city of Chicago played a central role in the development of the Midwest. The advent of the railway gradually reduced its importance, and nowadays it is largely recreational.
The Illinois Waterway was created by the construction (completed in 1848) of the 155 km/96 mi-long Illinois and Michigan Canal, which connected the South Branch of the Chicago River with La Salle, near the head of navigation on the Illinois River. The canal bypassed navigational obstructions on the Des Plaines River. In 1900, the network was greatly improved when the Chicago Sanitary and Ship Canal replaced the old canal for the 48 km/30 mi-long stretch between Chicago and Lockport. At the same time, engineers reversed the flow of the Chicago River by closing its outlet into Lake Michigan, thus causing it to flow into the Waterway. The Des Plaines River was improved below Lockport to its junction with the Kankakee River (forming the Illinois River) at Dresden, and the old canal fell into disuse. The Waterway, which took traffic from the Mississippi at Grafton, Illinois, only 62 km/38 mi above St Louis, made Chicago, rather than St Louis or other older river ports like Cincinnati, the key to Midwestern development. The Waterway gradually lost trade to the railways and, since 1959, the vast majority of commercial shipping entering and leaving the Great Lakes does so by way of the St Lawrence Seaway to the north, rather than using the Illinois Waterway.