After the American Revolution, weak U.S. seacoast defenses and the lessons of the War of 1812 led Congress to approve the Third System, a national program of forty-two brick and mortar forts built for local geography but sharing common materials and design theory. Fort Caswell was built as part of this system and, although it never saw large-scale military action during the Civil War, it served as a deterrent to Union attack, helping keep Wilmington open for trade longer than any other Confederate port. Built and maintained by the federal government, the fort fell in 1861 to a volunteer company led by a militia officer and became a Confederate stronghold. After the fall of Fort Pulaski showed that Third System forts were vulnerable to advanced artillery, Fort Fisher was built of earth three miles away and earthworks were added around Fort Caswell as well. Caswell commanded Old Inlet, the traditional route from the Atlantic Ocean to Wilmington, and deterred federal blockade movements against blockade runners. In February 1863, the USS Dacotah fired on a steamer passing near the fort at daybreak, and Fort Caswell's guns replied, causing one injury and one death aboard the assisting USS Monticello. After Fort Fisher fell to Union forces on January 15, 1865, Fort Caswell was cut off from practical resupply and Old Inlet was no longer strategically important to the Confederates. Retreating troops from Fisher withdrew to Caswell and prepared to destroy the fort they had held for almost four years without losing a single life to the enemy. Shortly after midnight on January 17, 1865, the citadel and wooden buildings were set on fire and fuses were lit to the magazine rooms. One magazine explosion caused damage still visible afterward, and another reportedly held close to 100,000 pounds of powder. Reports said the blast was felt thirty miles away in Wilmington and possibly as far as Fayetteville, one hundred miles away. James Erastus Price, who witnessed the scene from nearby Southport as a boy, later recalled a flash racing through the darkness toward the fort, followed by a volcanic burst of light, a roar, and a jar that shattered glass. In an instant, Fort Caswell was a ruin.
