Lake County has been inhabited by Pomo Native Americans for over ten thousand years.

Pomos had been fishermen and hunters, known especially for their intricate basketry made from lakeshore tules and other native plants and feathers.

Other crops include grain, alfalfa, hay, prunes, peaches, apples, grapes and walnuts.

With authorized cultivation limited to sacramental purposes, most of the vineyards were ripped out and replanted with walnut and pear orchards.

Numerous small faults are present in the south end of the lake as well as many old volcanoes, the largest being Cobb Mountain.

Lake County has habitats for a variety of species of concern including the uncommon herb, Legenere limosa, the rare Eryngium constancei, and the tule elk.

In 2015, President Barack Obama created the Berryessa Snow Mountain National Monument, incorporating these and other areas.

[16] Lake County has a Mediterranean climate with hot summer daytime temperatures in its lower elevations.

Lake County has been ranked by the American Lung Association as having the cleanest air in the nation, including in 2013, 2014 and 2015.

This county has gone through a growth in housing units, adding a sum of 1,414 residential structures since 2001, a change of 4.3 percent.

Lake County had a median home value in the year 2005 of $255,300, according to the American Community Survey.

In 2005, the American Community Survey reported that 14.4% of Lake County's owner-occupied dwellings are valued over a half a million dollars.

[41] Nonetheless, between 1920 and 1984 Lake County tended towards leaning Republican and was won by just four Democratic nominees – Franklin D. Roosevelt in 1932 and 1936, Lyndon B. Johnson in 1964 and Jimmy Carter in 1976.

[44] On November 4, 2008, Lake County voted 52.6% for Proposition 8, which amended the California Constitution to ban same-sex marriages.

CAL FIRE determined 8 wildfires in their jurisdiction in Lake County were caused by arson in 2023.

[51] The county's largest employers are the healthcare industry, Native American casinos, grocery stores, school districts, and electricity company Calpine, which operates in the Geysers geothermal field in the Mayacamas Mountains.

[52] The only significant manufacturing operations in Lake County are Stokes Ladders in Kelseyville, which builds orchard and industrial ladders,[53] and Reynolds Systems in Middletown, which specializes in detonators, igniters, precision initiating couplers, leads and boosters for the aerospace industry.

A reemergence of the wine industry began in the 1970s, although most of the region's grapes are still trucked to neighboring Napa, Sonoma and Mendocino counties for vinification.

The county saw its vineyard acreage increase from fewer than 100 acres (40 ha) in 1965 to more than 11,000 acres (4,500 ha) in 2023[57] The region is host to nine American Viticultural Areas, notably Guenoc Valley, High Valley and the Red Hills, and about 20 winery operations.

The county was once host to the Paul Hoberg Airport in the Cobb area, which by the early 1980s was considered abandoned.