Sierra Nevada (sēĕrˈə nəväˈdə) [key], mountain range, c.400 mi (640 km) long and from c.40 to 80 mi (60–130 km) wide, mostly in E Calif. It rises to 14,495 ft (4,418 m) in Mt. Whitney, the highest peak in the United States outside Alaska. The mountains extend NW from Tehachapi Pass near Bakersfield, Calif., to the gap S of Lassen Peak. A tilted fault-block in structure (the largest in the United States), the Sierra Nevada's eastern front rises sharply from the Great Basin, while its western slope descends gradually to the hills bordering the Central Valley of California. Heavy winter precipitation is economically important to the surrounding areas; snow-fed streams supply irrigation water to the Central Valley and to W Nevada and also generate hydroelectric power. High, rugged, and frequently snowbound in winter, the mountains are a formidable barrier to overland travel. Donner Pass (alt. 7,089 ft/2,161 m), the principal pass across the mountains, was used by thousands of California-bound gold-seekers and immigrants in the middle and late 1800s. The Sierra Nevada are known for their magnificent scenery (especially in the High Sierra S of Lake Tahoe and in Yosemite, Sequoia, and Kings Canyon national parks) and for their year-round resorts.