The first European and English settlers arrived here in 1713 in what was originally part of the colonial precincts of Carteret and New Hanover. Onslow County was formed in 1734 and was named for the Honorable Arthur Onslow, Speaker of the British House of Commons. After a lethal 1752 hurricane, the county courthouse was relocated from Town Point to Wantland's Ferry; this settlement was eventually incorporated in 1842 and named Jacksonville after President Andrew Jackson.

The county is home to more than 185,000 people and includes the incorporated towns of Holly Ridge, Richlands, Swansboro, North Topsail Beach, part of Surf City, and unincorporated Sneads Ferry. Approximately 156,000 acres comprise the U.S. Marine Corps Base, Camp Lejeune and more than 43,000 marines and sailors are stationed there.