Fort Frederica National Monument is the ruins of a fort and town built by James Oglethorpe. The fort was constructed between 1736 and 1748 to protect the southern boundary of the British colony of Georgia from Spanish raids. Fort Frederica gained a spot on the National Register of Historic Places in 1966. It's open every day from 9 a.m. to 5 p.m. and is managed by the National Park Service.