Both the first and the last actions of the war in Onslow County were to occur within the present area of Camp Lejeune. On 17 December 1861 a landing party from the USS Gemsbock put ashore on Cedar Point at the New River's mouth, near Captain Ward's plantation. Then, just one month prior to end of hostilities, the Union 2nd and 3rd Divisions, XXIII Corps, under Major General Darius N. Couch, marched through Onslow County en route to a rendezvous with General William T. Sherman and a final meeting with the remnants of the army of General Joseph E. Johnston. Onslow County's most storied Civil War engagement, the Battle of New River (23 to 25 November 1862), occurred within the boundaries of present-day Camp Lejeune. In this battle, the irrepressible William B. Cushing, United States Volunteer Navy, drove his iron-hulled screw steamer, the USS Ellis, into the New River's dangerous mouth and deceptive channels on the early morning of 23 November. His mission was to capture Jacksonville, seize any blockade runners, destroy salt works, and withdraw. Cushing completed his mission quickly, but in an attempt to escape encircling Confederates, he ran hard aground at the channel's mouth off Swan's Point, a victim of the same navigational limitations that had impeded Onslow's progress for 150 years. Under heavy fire from two Confederate cavalry companies and one of artillery, Cushing managed to blow up the Ellis and escape with his crew out of harm's way on 25 November and back out to the Atlantic.
Unlike previous conflicts, the Civil War thoroughly devastated Onslow County economically, socially, and physically. Most of the slaves remained in the county during the war, although some fled across the White Oak River to freedom, and some actively assisted in the war's efforts on both sides. With the war's conclusion, however, African Americans found themselves freed but without the means for survival. The area's landed aristocracy had virtually ceased to exist, and veterans returned to a war-torn landscape. It would require several generations before Onslow County and the Camp Lejeune area would recover socially and economically.