Sweetwater is a city in Monroe and McMinn counties in the U.S. state of Tennessee, and the most populous city in Monroe County. The population was 5,586 at the 2000 census. Sweetwater is the home of the Craighead Caverns which contains the Lost Sea, the United States' largest underground lake. Sweetwater is located at 35°36′9″N 84°28′1″W / 35.6025°N 84.46694°W / 35.6025; -84.46694 (35.602604, -84.466992). The city lies along Sweetwater Creek, which flows northeast for several miles before emptying into the Watts Bar Lake impoundment of the Tennessee River.