Keystone is a former settlement in Imperial County, California. It was located on the Southern Pacific Railroad 5 miles (8 km) north-northeast of Imperial.

Imperial County is a county located in the Imperial Valley, in the far southeast of the U.S. state of California, bordering both Arizona and Mexico. It is part of the El Centro Metropolitan Area, which encompasses all of Imperial County. The population as of 2010 was 174,528. The county seat is the city of El Centro. Established in 1907, it was the last county to be established in California. Imperial County is also part of the Southern California border region, also referred to as San Diego-Imperial, the smallest but most economically diverse region in the state.

Although this region is a desert, with high temperatures and low average rainfall of three inches (seventy-five mm) per year, the economy is heavily based on agriculture due to irrigation, supplied wholly from the Colorado River via the All-American Canal.

The Imperial Valley is a melting pot of European American and Hispanic cultures. On the American side, the majority of residents are of Mexican American heritage, while the Mexican side was greatly influenced by American culture for many decades. The entire valley is a multi-racial mixture of European Americans, East Asian Americans, South Asian Americans, some African Americans and Native Americans.

California (pronounced ⁱ/kælɨˈfɔrnjə/) is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third most extensive (after Alaska and Texas). It is home to the nation's second- and sixth-largest census statistical areas (Los Angeles Metropolitan Area and San Francisco Bay Area), and eight of the nation's fifty most populated cities (Los Angeles, San Diego, San Jose, San Francisco, Fresno, Sacramento, Long Beach and Oakland). The capital city is Sacramento.

California's diverse geography ranges from the Pacific Coast in the west, to the Sierra Nevada mountains in the east – from the Redwood–Douglas-fir forests of the northwest, to the Mojave Desert areas in the southeast. The center of the state is dominated by Central Valley, a major agricultural area. California contains both the highest and lowest points in the contiguous United States (Mount Whitney and Death Valley), and has the third-longest coastline of all states (after Alaska and Florida). Earthquakes are a common occurrence due to the state's location along the Pacific Ring of Fire: about 37,000 are recorded annually.