Onslow County's flat, rolling terrain covers and is located in the southeastern coastal plain of North Carolina, about east of Raleigh and north of Wilmington. The city of Jacksonville is the county seat, and the areas surrounding the city constitute the major population centers and growth areas in the county. The county is home to more than 150,000 people and includes the incorporated towns of Holly Ridge, Richlands, Swansboro, North Topsail Beach, part of Surf City, and unincorporated Sneads Ferry. The U.S. Marine Corps Base, Camp Lejeune, comprises roughly ; more than 43,000 marines and sailors are stationed there.