Lake Tahoe22 miles long, 1,645 feet deep, 6,225 feet above sea level — the largest alpine lake in North America

Lake Tahoe formed roughly two million years ago when a Sierra Nevada fault block dropped between two parallel uplifts, creating the basin that glaciers later deepened. The Washoe people, who spent summers here for at least the last 6,000 years, called the lake Da ow a ga — "edge of the lake" — which Anglo settlers later corrupted into the modern name. John C. Frémont "discovered" the lake for the United States on February 14, 1844; Mark Twain spent a transformative summer here in 1861 and described it in Roughing It as "the fairest picture the whole earth affords."

The lake is split between two states (about two-thirds in California, one-third in Nevada) and five counties. It holds 39 trillion gallons of water — enough to cover California 14 inches deep — at a measured purity of 99.994%, second only to Crater Lake among large North American lakes. The Secchi-disk-measured clarity has dropped from 102 feet in 1968 to about 70 feet today; the bi-state Tahoe Regional Planning Agency has been working since 1969 to halt and reverse that trend. Maximum depth is 1,645 feet (the second-deepest lake in the U.S.), the surface sits at 6,225 feet of elevation, and the surface-temperature swing is roughly 41°F in February to 68°F in August.

Plan four days minimum to see the lake well — one each for the South Shore (Heavenly Gondola, Emerald Bay), West Shore (D.L. Bliss, Sugar Pine Point, Tahoe City), East Shore (Sand Harbor, the East Shore Trail, Zephyr Cove), and North Shore (Kings Beach, Northstar, Crystal Bay). The 72-mile lakeshore loop drive takes about three hours without stops; expect six with photography. Summer brings traffic and parking pressure on summer weekends — use the East Shore Express shuttle and arrive at marquee beaches by 8 AM.