is located on the plains of the Texas Gulf Coast in the southeastern part of the state. The county is bounded on the northeast by Galveston Bay and on the northwest by Clear Creek and Clear Lake. Much of the county covers Galveston Bay, and is bounded to the south by the Galveston Seawall and beaches on the Gulf of Mexico.Galveston Bay
is located along Texas' upper coast. The Galveston Bay system consists of five subbays: Christmas Bay, West Bay, Lower Galveston Bay, Upper Galveston Bay, East Bay, and Trinity Bay.
The bay is fed by the Trinity River and the San Jacinto River, numerous local bayous and incoming tides from the Gulf of Mexico. The bay covers approximately 600 square miles, and is 30 miles long and 17 miles wide. Galveston Bay is on average 7-9 feet deep.
The bay has three inlets at the Gulf of Mexico: Bolivar Roads (the exit of the Houston Ship Channel) between Galveston Island and the Bolivar Peninsula, San Luis Pass to the West, and Rollover Pass to the East.
The Houston Ship Channel, connecting the Port of Houston to the Gulf, passes through Galveston Bay. Houston, Texas is the largest city on the bay, while smaller ones include Galveston, Pasadena, Baytown, Texas City, Anahuac and Port Bolivar. Four counties border the bay; Brazoria, Chambers, Harris, and Galveston County.