The St. Marys River (named Saint Marys River by the USGS, and sometimes misspelled as St. Mary's River) is a 126-mile-long (203 km) river in the southeastern United States. From near its source in the Okefenokee Swamp, to its mouth at the Atlantic Ocean, it forms a portion of the border between the U.S. states of Georgia and Florida. The river also serves as the southernmost point in the state of Georgia. The St. Marys River rises as a tiny stream, River Styx, flowing from the western edge of Trail Ridge, the geological relic of a barrier island/dune system, and ... Source: Wikipedia