About an hour south of St. Simons is Cumberland Island.
Cumberland Island is actually two islands—the island proper and Little Cumberland Island—connected by a marsh. As another Sea Island, Cumberland’s unspoiled natural beauty and rich wildlife make it a popular destination for visitors. Its biggest draw is the wild horses that roam the Island.
Reaching this island requires transportation by ferry. Cars aren’t allowed on Cumberland. Those who wish to explore can take a guided tour by van or choose a 4+mile self-guided walking around Southend Loop Trail. This is a great way to explore the island! The Southend Loop takes you through several ecosystems and provides access into some of its main historic districts.
Private properties on Cumberland Island are maintained with a nature and conservation mission for over 60 years. Historically, portions of Cumberland Island remain in private hands. Members or heirs of the Carnegie family deeded large areas to the National Parks Foundation by in 1971.
Carnegie Family era.
In the 1880s Thomas M. Carnegie, brother of steel magnate Andrew Carnegie, and his wife Lucy bought land on Cumberland for a winter retreat. In 1884, they began building a mansion on the site of Dungeness, though Carnegie never lived to see its completion. Lucy and their nine children continued to live on the island, naming their mansion Dungeness after that of Greene. Dungeness was designed as a 59-room castle.

After the Crash and the Great Depression, the family left the island and kept the mansion vacant. It burned in a 1959 fire, started by a poacher. Today, the ruins of the mansion remain on the southern end. The Carnegie family owned 90% of the Island.
Present-day conservation.
In 1954, some of the members of the Carnegie family invited the National Park Service to the island to assess its suitability as a National Seashore. In 1955, the National Park Service named Cumberland Island as one of the most significant natural areas in the United States and plans got underway to secure it. Simultaneously, the State of Georgia was working on plans to secure the Island as a state park.
In October 1968, Carnegie descendants sold three thousand acres of the Island to real estate developer Charles Fraser, who had developed part of Hilton Head Island, South Carolina. Fraser met with conservationist and then Sierra Club to discuss how to develop the area. The Club wanted 90% of the land to remain undeveloped.
Eventually, a bill through the US Congress established Cumberland Island as a national seashore. The Carnegie family sold the island to the federal government. With donations from the Mellon Foundation, Cumberland Island became a unit of the National Park Service, designated Cumberland Island National Seashore.
Funds provided by the Mellon Foundation and Congress purchased other lands in private ownership.
A small number of property owners, principally ones who preserved the island and protected it from massive commercial development, still own their homes and other private property on the southern, western and northern regions of the island.
Some, however, sold their property to the National Park Service (NPS), with an agreement that retains their ownership and full property rights during their lifetime.
Source: https://en.wikipedia.org/wiki/Cumberland_Island.