The Big River is a tributary of the Meramec River in east-central Missouri. The river rises in western Iron County near the summit of just north of Missouri Route 32 and approximately 3.5 miles southeast of the community of Enough. It flows through Washington, Saint Francois, and Jefferson counties. It forms part of the boundary between Jefferson and Saint Francois counties and also part of the boundary between Jefferson and Washington counties. It empties into the Meramec River opposite Eureka where the Meramec forms the border between Jefferson and Saint Louis counties. The river flows through Washington State Park, St. Francois State Park, and the Lead Belt mining district. The elevation of the river at its source is approximately 1,300 feet (400 m) above sea level and at its mouth abo