Area 51 the base extends further east. After leaving the restricted area, Groom Lake Road descends eastward to the floor of the Tikaboo Valley, passing the dirt-road entrances to several small ranches, before converging with State Route 375, the "Extraterrestrial Highway", south of Rachel. Area 51 shares a border with the Yucca Flat region of the Nevada Test Site, the location of 739 of the 928 nuclear tests conducted by the United States Department of Energy at NTS. The Yucca Mountain nuclear waste repository is southwest of Groom Lake. Groom Lake is a salt flat in Nevada used for runways of the
Ohio State Route 51 and US 223 end here as well. The original route of State Route 51 was that of current State Route 49 in western Ohio. The route was generally changed from 51 to 49 until the entire route became 49 in 1935. A new State Route 51 was certified in 1955, with its southern terminus where it is now and its northern terminus at then-State Route 120 (close to where I-280 is now) in Northwood. State Route 51 was extended to State Route 2 in Oregon in 1959. In 1989, State Route 51 replaced the route of U.S. Route 223 though