The Hennepin Canal

The Hennepin Canal in north-central Illinois was first conceived in 1834 as a connection between the Illinois and Mississippi Rivers but financial problems in the state delayed many public works projects. Pressure for transportation that was cheaper than rail convinced Congress to authorize preliminary surveys on the project in 1871. Construction began in 1892 and the first boat went through in 1907, reducing the distance from Chicago to Rock Island by 419 miles). While the canal was under construction, however, the Corps of Engineers undertook a widening of the locks on both the Illinois and Mississippi Rivers. The new locks on those rivers were twenty and forty feet wider than the canal locks, making them obsolete before their initial use. In the 1930s the Hennepin Canal was used primarily for recreational traffic. The Hennepin Canal, which at one time was known as the Illinois and Mississippi Canal, was open to boat traffic until 1951 at no cost. Ice made from the canal's frozen waters was sold during the winters to help pay the canal's maintenance costs. The Hennepin was the first American canal built of concrete without stone cut facings. Although the Hennepin enjoyed only limited success as a waterway, engineering innovations used in its construction were a bonus to the construction industry. The canal was used as a training ground for engineers that later worked on the Panama Canal. Both the Hennepin and Panama Canals used concrete lock chambers and both used a feeder canal from a man made lake to water the canals because both needed water to flow uphill. There are 33 locks on the canal. All are now visible, but the first one, on the Illinois River, had been under water from the 1930s until recent times. Fourteen of the locks had Marshall gates, which are unique to the Hennepin Canal, and were raised and lowered on a horizontal axis. Five of the locks have been restored to working condition, although they are not used. One of these is a Marshall Gate lock. All of the gates from the remaining locks have been replaced with concrete walls, creating a series of waterfalls.
The Hennepin originally had nine aqueducts – concrete troughs which carried the canal and its traffic across larger rivers and streams. Six of the aqueducts remain while the other three were replaced by pipes that carry the flow under the creek or river which the canal crossed.