Big Sandy is a town in Upshur County, Texas, United States. As of the 2010 census, the town's population was 1,343. A lake of the same name is cut nearly in half by U.S. Highway 80, the main thoroughfare of Big Sandy.The Sabine River flows just south of Big Sandy. In the 19th century, Walters' Bluff Ferry operated on the Sabine, with passage across costing 40 cents per person and up to 75 cents for wagons.