Nearly all of South Dakota drains into the Gulf of Mexico via the Missouri River, but the waters of the northeast corner flow north to the Red River Valley and onto Hudson Bay.  The Continental Divide that separates the two watersheds begins north of Britton and generally follows Highway 10 to Browns Valley, a marshy valley midway between Lake Traverse and Big Stone Lake. Traverse flows north and Big Stone flows south. A sign on Britton’s Main Street denotes the unusual geographic feature, and the city’s Prayer Rock Museum has related exhibits. The Continental Divide, one of only five in North America, ranks among the most interesting and scenic features in a state known for geological variety.