Sand Lake National Wildlife Refuge is a protected wetland in northeastern South Dakota established in 1935 to conserve breeding grounds and wildlife habitat after settlement and farming damaged the region’s marshes and contributed to declining waterfowl. Managed by the U.S. Fish and Wildlife Service, it spans about 21,498 acres around Sand Lake, Mud Lake, and the James River. Civilian Conservation Corps dams helped create Sand Lake and Mud Lake during the New Deal era. The refuge is a major bird habitat, with more than 260 recorded species, the world’s largest breeding colony of Franklin’s gulls, Ramsar recognition for international importance, and designation as a Globally Important Bird Area.