There are 136 Federal harbors within the Great Lakes Basin, with 745 miles of navigation channels. A "Federal" channel or harbor is one that has been authorized by Congress. Most of these navigation authorizations date from the early 19th century. These harbors and channels were constructed to serve commercial navigation, recreational navigation, or both.
Channels and harbors are maintained for safe navigation. The depths of channels vary with the types of traffic. The navigation channels on the Mississippi and Ohio Rivers are maintained at authorized depths of 9 feet, which is sufficient for the barges and cargo they carry on these rivers. In contrast, the Connecting Channels between the Great Lakes are maintained at depths of 30 feet for the ocean-going ships which carry ore, coal, and other cargos between domestic and international ports. The channels at a particular harbor may have depths up to 30 feet at the entrance with progressively shallower depths as one moves upstream. This is especially common at harbors where commercial navigation is concentrated near the river mouth while recreation traffic extends a distance upstream.
In order to maintain channels and harbors at safe depths, periodic dredging is required. Great Lakes harbors and channels are maintained by the Corps' districts in:
- Buffalo District (harbors in New York, Pennsylvania and Ohio)
- Chicago District (harbors in Indiana and Illinois)
- Detroit District (harbors in Michigan, Wisconsin and Minnesota)