Antietam Creek, one of Antietam National Battlefield’s most significant natural features, is an important historical landmark, a tributary of the Potomac River, and a popular recreational spot. Nearly three miles of the creek and about one mile of its tributaries are located within the park’s boundaries. About two miles south of the park, the creek’s waters flow into the Potomac River, which becomes one of the largest tributaries of the Chesapeake Bay, the nation’s largest and most productive estuary.