At over twelve-miles long and roughly one-mile wide Oak Island is Brunswick County's largest island. It is situated adjacent to the historic town of Southport, and due to the arc of Brunswick County's islands, Oak Island's beaches actually face southward to the Bahamas rather than eastward toward Africa. Modern occupancy of the island traces back to the construction of Fort Caswell, which was occupied by Confederate troops during the Civil War. In 1889, the Oak Island Lifesaving Station was completed and together these two installations marked the first "permanent" settlements on the island. In the 1930s commercial development of the island began; until then the only frequent visitation to the area was made by fox hunters. Although it has always been referred to as an island, its status was not official until the Atlantic IntraCoastal Waterway was dredged in 1936. In 1955 the towns of Long Beach and Yaupon Beach were incorporated. These two towns merged in 1999 to form the Town of Oak Island.
The Oak Island Lighthouse was completed in 1958. It stands over 169-feet above sea level and at the time of its activation it featured the second brightest flash in the world. Caswell Beach, which is home to the lighthouse, was incorporated in 1975. Oak Island also hosts a U.S. Coast Guard Station.
Oak Island is also a hotspot for Atlantic sea turtles, and every year varieties such as the Green, the Loggerhead and the Kemp Ridley make their way to the island to nest. A joint project was recently completed with the US Army Corps of Engineers to restore habitat for sea turtles.