The Monongahela River runs north from the confluence of the West Fork and Tygart rivers at Fairmont, West Virginia. It flows through the coal fields and mountains of West Virginia and into Western Pennsylvania where, in its valley, lies one of the great industrial areas of the country. The Mon joins the Allegheny River at Pittsburgh to form the Ohio River.

Boatbuilding was the first industry on the Mon. Shipwrights from the East established several boatyards to utilize the abundant timber and construct boats for the westward migration down the Ohio. After the Revolutionary War, western farmers and traders began to ship goods downriver to New Orleans, dismantling the boats for lumber at the end of the one-way trip. Agents of Robert Fulton, inventor of the steamboat, launched a river steamer on the Mon near Pittsburgh in 1811, the first of thousands built here until the 1880s.

In 1837, after years of planning, the Monongahela Navigation Company, chartered by the Commonwealth of Pennsylvania, began building a series of seven locks and dams from Pittsburgh towards the West Virginia state line. The federal government followed suit and began building eight additional locks and dams upriver as far as Fairmont, West Virginia. Boats paid tolls to use the company locks, but the government's were free to all traffic.

The government eventually bought the Pennsylvania locks from the navigation company in 1897, making the Mon a toll-free navigation system to Pittsburgh. The present Mon navigation system has nine locks and dams of several sizes and types constructed by the U.S. Army Corps of Engineers between 1902 and 1994. These locks allow boats to travel in a series of steps down the 147-foot difference in pool elevation from Fairmont to Pittsburgh.

The locks and dams on the Mon enable it to carry as much tonnage as the flat lowland rivers of Europe like the Rhine and the Thames. The lower six locks transport most of the heavy traffic, largely coal moving both downstream and upstream to steel mills and power plants.

Most of the companies along the Mon use the river for shipping and depend on the pool for a reliable water supply. Tygart Lake, in the headwaters of the Mon, was built by the Corps to provide a more dependable supply of water in case of drought on this important waterway.