A national recreation area (NRA) is a protected area in the United States established by an Act of Congress to preserve enhanced recreational opportunities in places with significant natural and scenic resources. There are 40 NRAs, which emphasize a variety of activities for visitors, including hiking, camping, boating, fishing, swimming, biking, horseback riding, and wildlife viewing, in areas that include multiple-use management for both conservation and limited utilization of natural resources. They have diverse features and contexts, being established around reservoirs, in urban areas, and within forests. Due to their size, diversity of activities, and proximity to population centers, NRAs are among the most visited units of the National Park System, with six among the thirty most visited sites. The first NRA was Lake Mead National Recreation Area, which was created by a 1936 agreement between the United States Bureau of Reclamation (USBR), which had built Hoover Dam, and the National Park Service (NPS), which had experience in managing visitors in the outdoors. Because the reservoir had disturbed the natural state of the environment, a new designation was devised that allowed for more intensive land use while maintaining the NPS's role in conservation and historic preservation. The system of NRAs grew as the USBR constructed more dams near urban areas where there was a need for outdoor recreation. NRAs are managed by the NPS, the United States Forest Service (USFS), and the Bureau of Land Management (BLM). Of the NPS's 18 sites, 12 are based around large reservoirs emphasizing water recreation, 5 are near urban areas and include both historic preservation and outdoor recreation, and the last is at a river where a reservoir was planned but not built. Of the USFS's 22 sites, 5 are at or near reservoirs, and the rest are other exemplary recreation sites within national forests. The 40 NRAs are located in 26 states; California and Washington have the most, each with four. NRAs of the USFS have a total area of , and those of the NPS total . The BLM's one NRA is approximately . History Origin The U.S. Bureau of Reclamation was planning the construction of Boulder Dam (now Hoover Dam) on the Colorado River in the late 1920s and saw the potential for recreation at the scenic area in Nevada and Arizona around the future Lake Mead, to then be the world's largest reservoir. The car was expanding access to travel