The county extends east beyond the southern slope of the Eastern Sierra Nevada range into the Mojave Desert, and includes parts of the Western Indian Wells Valley, and Northern Antelope Valley, north of Los Angeles County, an area larger than the state of Massachusetts. From the Sierra's the county extends across the floor of the San Joaquin Valley to the eastern edge of the Temblor Range, part of the Coastal Ranges. To the south the county extends over the ridge of the Tehachapi Mountains.

Kern County enjoys a moderate climate with generally mild temperatures throughout the year. 100+ temperatures occur about 38 days per year while below freezing temperatures only happen on twelve days per year. There are usually 223 sunny days every year. The county has several general climate areas including valley, mountain and high desert.

In 1772, Commander Don Pedro Fages was the first European to come to the area that had been claimed by the Spanish in 1769. In 1848, the Treaty of Guadalupe Hidalgo was enacted bringing California, Nevada and Utah into the United States. The county was created in 1866 but not much development occurred due to its swamps, lakes and diseases like malaria that went along with the terrain. Once hardy settlers arrived and began to drain the land for farming and making canals to direct the water, the area attracted more people. Before this time the major activity was mining but after the improvements, mostly completed by Chinese laborers, the community areas and their businesses, along with agriculture, began to take over as the major portions of the county's economy.

The first county seat was the mining town of Havilah in the mountains between Bakersfield and Tehachapi. The county seat was moved from Havilah to Bakersfield in 1874. For the most part, the new settlers and the native inhabitants of the area meshed together well, but a few incidents stand out. Most well-known was the slaughter of five Indians in 1856 and the Keyesville Massacre in 1863 where 35 Indians were killed by soldiers. Some of the native tribes were the Mohave, Paiute and Yokuts. The Yukuts have mostly disappeared and the Paiute live mainly in the mountain areas. There are no reservations in the county area..

When the county was created in 1866, it was carved out of portions of both Los Angeles and Tulare Counties. The name for the county came from the Kern River. The river was named for Edward Kern who was a topographer for the 1845 expedition of John C. Fremont. Fort Tejon was built at the top of the Grapevine Canyon in the early 1850's near what is now Lebec. It was built to protect the peaceful Indians in the area from the more hostile Mohave and Paiutes. Today is is a state historic park.

A large earthquake hit the area on 21 July 1952, measuring 7.3 on the Richter scale. Twelve people were killed. Much damage occurred as well as numerous injuries. It was on the White Wolf Fault and was second in size to the 1906 San Francisco earthquake. The military and government-related industry in the county remains large. Edwards Air Force Base is the Air Force main flight test facility. The first landing of the Space Shuttle was here at Edwards. The Mojave Spaceport and the China Lake Naval Air Weapons Station are also located here.

This page lists the names of communities and areas within the county, some of which don't even exist anymore except in memory. Some have been absorbed into larger cities and some are very tiny places.

The county has a large agricultural base and is a significant producer of oil, natural gas, hydro-electric power, wind-turbine power, and geothermal power. As of 2004, Kern remains California's top oil-producing county, with over 85% of the state's 43,000 oil wells. The county accounts for one-tenth of overall U.S. oil production, and three of the five largest U.S. oil fields are in Kern County. Kern is also noted for its mineral wealth, including gold, borite, and kernite. Edwards Air Force Base, China Lake Naval Air Weapons Station, and Mojave Spaceport are located in Kern County (the latter being owned and operated by the county itself.) The Tehachapi wind resources area generates almost half of the wind energy produced in the state of California, providing approximately 1% of the states overal electricity needs.