Fort Jackson, named for one of the early governors of Georgia, is located on Salters Island, on the Savannah River. While Fort Pulaski guarded the mouth of the Savannah River, enemies could by-pass that entrance through rivers from the north and south. But no one could attack Savannah from the ocean without traveling past Salter Island - the site chosen for Fort Jackson. In addition to its strategic location, it offered deep water for off-loading troops and supplies and was protected by marsh.

Salters Island was first a brickyard belonging to Thomas Salter in 1741. During the 1770s it was the site of an earthen battery called Mud Fort that was used during the Revolutionary War. Later, President Thomas Jefferson decided that a national system of coastal fortification was needed to protect the young nation. The original brick fort on Salters Island was begun in 1808 by the U.S. Army Corps of Engineers under Captain William McRee and was used by local militia and federal troops as a signal station during the War of 1812.

Fort Jackson was enlarged and strengthened between 1845 and 1860, when engineers built the moat and drawbridge, brick barracks, privies, rear wall, and powder magazine. The fort has 20-foot-high walls, and a 9-foot- deep moat. It held nine cannons: five 32-pound smooth bore, one 32-pound rifled, two 8-inch Columbiads, and one mountain howitzer. A 32-pounder is still fired in demonstrations; it is the largest black powder cannon still fired in the United States.

While the surrounding marsh protected Fort Jackson from land attack, it also brought the mosquito-borne diseases of yellow fever and malaria. The fort was described in 1819 as "the most distempered spot in the universe." Consequently, the Fort Jackson garrison was housed in Savannah from May to November. The fort was abandoned during the Revolutionary War due to malaria, allowing the British to sail up the river and capture Savannah easily.

During the Civil War, Fort Jackson became the Confederate headquarters for the Savannah River defenses. Robert E. Lee, Jefferson Davis, and P.G.T. Beauregard all visited this fort. This inner line of defense consisted of Fort Jackson, the Savannah River Squadron, and a network of earthen batteries and signal stations along the marsh and waterways between Savannah and Wilmington rivers, as well as river obstructions and underwater mines.

Even after the fall of Fort Pulaski on Cockspur Island to Union troops on April 11, 1861 and the 40,000 Union troops on nearby Hilton Head, the Savannah River defenses kept Savannah safe from Federal forces attacking from the sea. Savannah was not surrendered until December 21, 1864, when Union Gen. William Tecumseh Sherman, on his famous March to the Sea, captured Fort McAllister on the Ogeechee River. However, on the night of December 20, 1864, the garrisons of Causton Bluff, Thunderbolt, and the Savannah River batteries gathered at Fort Jackson and evacuated across the Savannah River by steamer and on makeshift bridges. They continued to fight Sherman's army until they surrendered at Durham Station, North Carolina on April 26, 1865.

Three hundred yards away from Fort Jackson, a red buoy in the Savannah River can be seen marking the remains of the Savannah-made C.S.S. Georgia. She was scuttled by her crew on the night of Savannah's evacuation to prevent it from falling into Union hands. It was Georgia's first ironclad, launched May 19, 1862, and stationed downstream from Fort Jackson as a floating battery with its ten heavy guns.