The Mobile River is located in southern Alabama in the United States. Formed out of the confluence of the Tombigbee and Alabama rivers, the approximately 45-mile-long (72 km) river drains an area of 44,000 sq mi (115,000 kmĀ²) of Alabama, with a watershed extending into Mississippi, Georgia, and Tennessee. Its drainage basin is the fourth-largest in the United States. The river has historically provided the principal navigational access for Alabama. Since construction of the Tennessee-Tombigbee Waterway, it also provides an alternative route into the Ohio River watershed. The Tombigbee and Alabama River join to form the Mobile River approximately 50 mi (80 km) NNE of Mobile, along the county line between Mobile and Baldwin counties. The combined stream flows south, in a winding course. Approximately 6 mi (10 km) downstream from the confluence, the channel of the river divides, with the Mobile flowing along the western channel. The Tensaw River, a bayou of the Mobile River, flows alongside to the east, separated from 2 to 5 mi (3 to 8 km) as they flow southward. The Mobile River reaches Mobile Bay on the Gulf of Mexico just east of downtown Mobile.