Caddo Lake is a 25,400-acre (10,300 ha) lake and bayou (wetland) on the border between Texas and Louisiana, in northern Harrison County and southern Marion County in Texas and western Caddo Parish in Louisiana. The lake is named after the Caddoans or Caddo, Native Americans who lived in the area until their expulsion by the United States in the 19th century. The US forced most of them to move west to Indian Territory.

Harrison County is a county on the eastern border of the U.S. state of Texas. As of the 2020 United States census, its population was 68,839. The county seat is Marshall. The county was created in 1839 and organized in 1842. It is named for Jonas Harrison, a lawyer and Texas revolutionary.