Fine geological map of Lake Lahontan, published by the US Geological Survey.
Lake Lahontan was a large endorheic Pleistocene lake, located in modern northwestern Nevada. The area of the former lake is a large portion of the Great Basin that borders the Sacramento River watershed to the west.
The lake was at its peak size about 10,600 B.C., at which time it covered over 8,500 square miles. Climate change around the end of the Pleistocene epoch resulted in a gradual decline in the size of Lake Lahontan. The lake had largely disappeared by about 9,000 years ago. Over time, the lake broke up into a series of smaller lakes, most of which rapidly dried up, leaving only a playa. These playas include the Black Rock Desert, the Carson Sink, and the Humboldt Sink. The only modern remnants existing as true lakes are Pyramid Lake and Walker Lake. Winnemucca Lake has been dry since the 1930s.