The San Joaquin River eventually meets the Sacramento River, forming the Sacramento-San Joaquin Delta. This is one of the biggest estuaries in the United States. It is near the city of Antioch. At this place, the San Joaquin River splits into two rivers: the "Old River" and the "Middle River". The Old River sometimes confuses fish to go down its channel. As a result, a wall is built between the San Joaquin River and the Old River.