Which river is Old Fort Jackson located on?

Old Fort Jackson is located on the Savannah river.

Savannah River was called after the Shawnee, an Algonquian people, who are still estimated to be 14 000 people. The Savannah river forms the border between Georgia and South Carolina, and is about 300 miles long. Old Fort Jackson is located about 6 km from the mouth of Savannah, on its southern shore.