The river rises in a region of granite mountains in Iron County, Missouri, and flows generally southwardly through the Ozarks and the St. Francois Mountains near Missouri's highest point Taum Sauk. It forms the Missouri-Arkansas border in the Bootheel and eventually exits the state at Missouri's lowest point in the toe at above sea level. It passes through Lake Wappapello, which is formed by a dam constructed in 1941. Below the dam the river meanders through cane forests and willow wetlands or forested swamp, transitioning from a clear stream into a slow and silt-laden muddy river as it enters the flat lands of the Mississippi embayment. In its lower course the river parallels Crowleys Ridge and is part of a navigation and flood-control project that encompasses a network of diversion channels and ditches along it and the Castor and Little rivers. Below the mouth of the Little River in Poinsett County, Arkansas, the St. Francis is navigable by barge. It joins the Mississippi River in Phillips County, Arkansas, about north of Helena.