It was built near Charleston, South Carolina, as one of the third system of U.S. fortifications to protect American harbors from a naval invasion.

It was one of a number of special forts planned after the War of 1812, combining high walls and heavy masonry, and classified as Third System, as a grade of structural integrity.

The First Battle of Fort Sumter began on April 12, 1861, when South Carolina Militia artillery fired from shore on the Union garrison.

Although the fort was reduced to rubble, it remained in Confederate hands until it was evacuated as General Sherman marched through South Carolina in February 1865.

The fort was not yet complete at the time and fewer than half of the cannons that should have been available were in place, due to military downsizing by President James Buchanan.

"[12] Over the next few months repeated calls for evacuation of Fort Sumter[8]: 13 [13] from the government of South Carolina and then from Confederate Brigadier General P. G. T. Beauregard were ignored.

Union attempts to resupply and reinforce the garrison were repulsed on January 9, 1861, when shots fired by cadets from the Citadel prevented the steamer Star of the West, hired to transport troops and supplies to Fort Sumter, from completing the task.

Artillery, and three hired tugboats with added protection against small arms fire to be used to tow troop and supply barges directly to Fort Sumter.

[8]: 304 On Thursday, April 11, 1861, Beauregard sent three aides, Colonel James Chesnut, Jr., Captain Stephen D. Lee, and Lieutenant A. R. Chisolm to demand the surrender of the fort.

At about 3:00 a.m., when Anderson finally announced his conditions, Colonel Chesnut, after conferring with the other aides, decided that they were "manifestly futile and not within the scope of the instructions verbally given to us."

Edmund Ruffin, noted Virginian agronomist and secessionist, claimed that he fired the first shot on Fort Sumter.

Accounts, such as in the famous diary of Mary Chesnut, describe Charleston residents along what is now known as The Battery, sitting on balconies and drinking salutes to the start of the hostilities.

Union efforts to retake Charleston Harbor began on April 7, 1863, when Rear Admiral Samuel Francis Du Pont, commander of the South Atlantic Blockading Squadron, led the ironclad frigate New Ironsides, the tower ironclad Keokuk, and the monitors Weehawken, Passaic, Montauk, Patapsco, Nantucket, Catskill, and Nahant in an attack on the harbor's defenses.

The attack was unsuccessful: the Union's best ship, USS New Ironsides never effectively engaged, and the ironclads fired only 154 rounds, while receiving 2,209 from the Confederate defenders (Wise 1994, p. 30).

Due to damage received in the attack, the USS Keokuk sank the next day, 1,400 yards (1,300 m) off the southern tip of Morris Island.

Over the next month, working at night to avoid the attention of the Federal squadron, the Confederates salvaged Keokuk's two eleven-inch Dahlgren guns (Ripley 1984, pp. 93–96).

A workforce of just under 500 enslaved Africans, under the supervision of Confederate army engineers, were filling casemates with sand, protecting the gorge wall with sandbags, and building new traverse,[17] blindages,[18] and bombproofs.

After the devastating bombardment, both Major General Quincy A. Gillmore and Rear Admiral John A. Dahlgren, now commanding the South Atlantic Blockading Squadron, determined to launch a boat assault on Fort Sumter for the night of September 8–9, 1863.

Dahlgren refused to place his sailors and Marines under the command of an army officer, so two flotillas set out towards Fort Sumter that night.

This underestimation of the Confederate forces on Dahlgren's part may explain why he was hostile to a joint operation wishing to reserve the credit for the victory to the navy.

After the unsuccessful boat assault, the bombardment recommenced and proceeded with the varying degree of intensity, doing more damage to Fort Sumter until the end of the war.

The Confederates continued to salvage guns and other material from the ruins and harassed the Union batteries on Morris Island with sharpshooters.

The last Confederate commander, Major Thomas A. Huguenin, a graduate of The Citadel, never surrendered Fort Sumter, but General William Tecumseh Sherman's advance through South Carolina finally forced the Confederates to evacuate Charleston on February 17, 1865, and abandon Fort Sumter.

Anderson, now a major general, returned to Sumter with the flag he had been forced to lower four years earlier, and on April 14, 1865, raised it in triumph over the ruined fort.

The start of the Spanish–American War prompted renewed interest in its military use and reconstruction commenced on the facilities that had further deteriorated over time.

A new massive concrete blockhouse-style installation was built in 1898 inside the original walls, armed with two 12-inch M1888 guns, one on a disappearing carriage.

[20] One hundred and forty-seven years after it was sent, a rolled up telegraphic message was found in a trunk belonging to Col. Alexander Ramsay Thompson of New York and eventually given to a museum in Charleston, S.C.

The telegram was dated April 14, 1861 from the Governor of South Carolina to Gazaway Bugg Lamar in New York, reading in part:[21] Fort Sumter surrendered yesterday after we had set all on fire... F.W.

[24] The Visitor Education Center's museum features exhibits about the disagreements between the North and South that led to the incidents at Fort Sumter.

[25] By December 2019, sea level rise led to a Park Service decision to move some of the large rocks "originally installed to protect the fort from the sea," farther from the fort's walls, in order to create a protective breakwater and wetland.