Tahoe, Lake (täˈhō, tāˈ–) [key], 193 sq mi (500 sq km), on the Calif.-Nev. line. It occupies a basin in the Sierra Nevada and is drained by the Truckee River. Lying 6,228 ft (1,898 m) above sea level, its depth (1,645 ft/501 m) prevents it from freezing. Long known for its clearness, the lake, explored in 1844 by John Frémont, had grown less so by the late 1990s, when government officials began efforts to restore it. Lake Tahoe is a major vacation spot, with gambling resorts along the Nevada shoreline.