Jefferson County is a county in the Coastal Plain or Gulf Prairie region of Southeast Texas. The Neches River forms its northeastern boundary. As of the 2020 census, the population was 256,526. The county seat is Beaumont. Jefferson County has the highest percentage of African Americans in the state of Texas.

The Neches River begins in Van Zandt County west of Rhine Lake and flows for 416 miles (669 km) through the piney woods of east Texas, defining the boundaries of 14 counties on its way to its mouth on Sabine Lake near the Rainbow Bridge. Two major reservoirs, Lake Palestine and B. A. Steinhagen Reservoir are located on the Neches. The Angelina River is a major tributary with its confluence at the north of Lake B. A. Steinhagen. Tributaries to the south include Village Creek and Pine Island Bayou, draining much of the Big Thicket region, both joining the Neches a few miles north of Beaumont. Towns and cities located along the river including Tyler, Lufkin, and Silsbee, although significant portions of the Neches River are undeveloped and flow through protected natural lands. In contrast, the lower 40 miles of the river are a major shipping channel, highly industrialized, with a number of cities and towns concentrated in the area including Beaumont, Vidor, Port Neches, Nederland, Groves, and Port Arthur.