The Meramec River is one of the longest free-flowing waterways in Missouri—it wanders some 220 miles (350 kilometers) through six Missouri Ozark Highland counties: Dent, Phelps, Crawford, Franklin, Jefferson, and St. Louis, before it empties into the Mississippi River at Arnold, Missouri and Oakville, Missouri. Between its source and its mouth, it falls 1,025 feet (313 m). The Meramec watershed covers portions of eight additional counties—Maries, Gasconade, Iron, Washington, Reynolds, St. Francois, Ste. Genevieve, and Texas—totaling approximately 3,980 square miles (10,300 square kilometers). Year-round navigability begins above Meramec Spring, just south of St. James. The Meramec's size increases at the confluence of the Dry Fork, and its navigability continues until the river enters the Mississippi at Arnold, Missouri.
The first European explorer was French Jesuit priest Jacques Gravier, who traveled the river in 1699–1700, and reports that the name means 'the river of ugly fishes' or 'ugly water' in Algonquian. Early variant spellings of the name were Mearamigoua, Maramig, Mirameg, Meramecsipy, Merramec, Merrimac, Mearmeig, and Maramecquisipi. The river early on became an important industrial shipping route, with lead, iron, and timber being sent downstream by flatboat and shallow-draft steamboat. The river is also the site of many canoe outfitters and ferry boat excursions. Today, the river is used commercially by tourboats and sand and gravel mining barges.
The river was listed at one time as one of the most polluted rivers in Missouri. Local and state government along the river have taken tremendous steps in cleaning it up. Today the river is one of the most diverse waters in Missouri. The river is plentiful in; black crappie, channel catfish, flathead catfish, largemouth bass, paddlefish, rainbow trout, brown trout, rock bass, smallmouth bass, walleye, white crappie, and some of the richest mussel beds in the state. The endangered Ozark Hellbender (Cryptobranchus alleganiensis bishopi) also lives in the river.
The Meramec River includes one of only three Red Ribbon Trout Areas in the state of Missouri, boasting a healthy rainbow trout population and an impressive brown trout population. Red Ribbon trout streams are managed by the Missouri Department of Conservation to produce trophy-sized fish.
Occasionally the river's name is mistakenly translated to mean "river of death", but this is probably in reference to the number of accidental drownings that occur in it every year.
The free-flowing Meramec River narrowly avoided having several dams built on it by the Corps of Engineers. The United States Congress authorized several large dams in the upper Mississippi and Meramec river basins in 1938 following severe flooding in both 1927 and 1937. The war intervened, plans were delayed and altered, but the Meramec Basin Project finally started moving forward in the 1960s. The main dam was to be at Sullivan, Missouri, at Meramec State Park, with several additional dams upstream. However, these plans ran into opposition from the growing environmental movement of the 1960s and 1970s, as well as from recreational users of the free-flowing Meramec. The failure of the Teton Dam in 1976 increased the public's doubt about the wisdom of the project.
Grass-roots opposition forced politicians originally in favor of the project to reconsider. At the request of Senators Jack Danforth and Tom Eagleton, Missouri Governor Kit Bond allowed a non-binding referendum to be put on ballots in twelve surrounding counties, and on August 8, 1978, sixty-four percent of the voters rejected the dam proposal. The referendum carried no legal weight but caused Congress to reconsider. Under President Jimmy Carter, funding was removed from the project, and in 1981, President Ronald Reagan signed the bill finally de-authorizing the project. This was the first time that a Corps of Engineers project was stopped once construction had already begun, and marked a major victory for the American environmental movement.