 Sweetwater is the home of the Craighead Caverns which contains the Lost Sea, the United States' largest underground lake.A legend states that the town's name originated from settlers’ descriptions of area springs.Sweetwater was established in the 1850s on a series of lots sold by Isaac Lenoir (1807–1875), a local politician and son of the founder of Lenoir City (located a few miles to the northeast in Loudon County).