Sapelo is about 12 miles long and two to four miles wide with a total area of 17,950 acres, making it the fourth largest of Georgia's barrier islands. Sapelo has 10,900 acres of uplands and five and one-half miles of undeveloped beaches. Sapelo's Nannygoat beach is noted for having the most extensive undisturbed natural beach dunes of any of Georgia’s barrier islands.
Sapelo Island is jointly owned by the State of Georgia, the R.J. Reynolds Foundation and the residents of the Hog Hammock Community. Sapelo is a National Estuarine Research Reserveand Wildlife Refuge. The Department of Natural Resources, the National Oceanic and Atmospheric Administration and the R. J. Reynolds Wildlife Refuge share the management duties of the island. At the south end of Sapelo, the University of Georgia Marine Institute conducts research in barrier island formation and salt marsh ecology. Primitive camping and short term lodging is offered through the residents of Hog Hammock and the DNR.