Tybee National Wildlife Refuge was established on May 9, 1938, by an executive order of President Franklin D. Roosevelt, as a breeding area for migratory birds and other wildlife. Located in the mouth of the Savannah River, the 100-acre (0.40 km2) refuge began as a 1-acre (4,000 m2) oyster shoal, Oysterbed Island, used by the U.S. Army Corps of Engineers as a spoil disposal site to support their mandated harbor dredging activity. As a result, the majority of the refuge is now covered with sand deposits. The more stable portions of the island are densely covered with such woody species as eastern red cedar, wax myrtle, and groundsel. Saltwater marsh borders parts of the island.