The State of California is the most populous state of the United States of America. Located on the Pacific coast of North America, it is bordered by Oregon, Nevada and Arizona in the United States, and Baja California in Mexico. The state's four largest cities are Los Angeles, San Diego, San Jose and San Francisco. California is known for its diverse climate and ethnically diverse population. The state has 58 counties.

The California Gold Rush, beginning in 1848, dramatically changed California with an influx of population and an economic boom, and San Francisco became a financial and cultural center. The early part of the 20th century was marked by Los Angeles becoming the center of the entertainment industry, in addition to the growth of a large tourism sector in the state. The Central Valley is home to California's important agricultural industry, the largest of any state. Other important industries have included the aerospace and oil industries. In recent decades, California has become a global leader in computers and information technology. If California were a country, its economy would rank among the ten largest in the world, and it would be the 35th largest country by population.

The word California originally referred to the entire region composed of the current U.S. state of California, plus all or parts of Nevada, Utah, Arizona, and Wyoming, and the Mexican peninsula now known as Baja California.

California borders the Pacific Ocean, Oregon, Nevada, Arizona, and the Mexican state of Baja California. With an area of 160,000 square miles (411,000 km²) it is the third largest state in the United States and is a little larger than Germany in size.

California's geography is rich, complex, and varied. In the middle of the state lies the California Central Valley, bounded by the coastal mountain ranges in the west, the Sierra Nevada to the east, the Cascade Range in the north and the Tehachapi Mountains in the south. The Central Valley is California's agricultural heartland and grows about 1/3 of the United States's food.[7] The northern half is known as the "Sacramento Valley" (drained by the Sacramento River), while the southern part of the valley is known as the "San Joaquin Valley" (drained by the San Joaquin River). With dredging, the Sacramento and the San Joaquin Rivers have remained sufficiently deep that several inland cities are seaports. The Sacramento-San Joaquin Bay Delta serves as a critical water supply hub for the state. Water is routed through an extensive network of canals and pumps out of the delta, that traverse nearly the length of the state, including the Central Valley Project, and the State Water Project. Water from the Sacramento-San Joaquin Bay Delta provides drinking water for nearly 23 million people, almost 2/3 of the state's population, and provides water to farmers on the west side of the San Joaquin Valley. The Channel Islands are located off the southern coast.