California is a U.S. state in the Western United States that lies on the Pacific Coast. It borders Oregon to the north, and Nevada and Arizona to the east; it also shares an international border with the Mexican state of Baja California to the south. With over 39 million residents across an area of 163,696 square miles (423,970 km2), it is the largest U.S. state by population and third-largest by area.
Prior to European colonization, California was one of the most culturally and linguistically diverse areas in pre-Columbian North America. European exploration in the 16th and 17th centuries led to the colonization by the Spanish Empire. The area became a part of Mexico in 1821, as a result of its successful war for independence. Following the U.S. conquest of California, part of the Mexican-American War, California was ceded to the United States in 1848. The California gold rush started in 1848 and led to social and demographic changes, including the California genocide. It organized itself and was admitted as the 31st state in 1850 as a free state, following the Compromise of 1850.
Greater Los Angeles and the San Francisco Bay Area are the nation's second and fifth most populous combined statistical areas. Los Angeles is the state's most populous city and is ranked second in population in the nation. California's capital is Sacramento. Part of the Californias region of North America, the state's diverse geography ranges from the Pacific Coast and metropolitan areas in the west to the Sierra Nevada mountains in the east, and from the redwood and Douglas fir forests in the northwest to the Mojave Desert in the southeast. Two-thirds of the nation's earthquake risk lies in California. The Central Valley, a fertile agricultural area, dominates the state's center. The large size of the state results in climates that vary from moist temperate rainforest in the north to arid desert in the interior, as well as snowy alpine in the mountains. While California is warming and drying overall, with frequent wildfires, the state is also experiencing increasing weather whiplash.
The economy of California is the largest of any U.S. state, with an estimated 2025 gross state product of $4.296 trillion as of Q3 2025. It is also the world's largest sub-national economy and, if it were an independent country, would be the fourth-largest economy in the world (behind Germany and ahead of Japan) by nominal GDP as of 2025. The state's agricultural industry leads the nation in output, fueled by its production of dairy, almonds, and grapes. Despite heavy reliance on seaborne foreign crude oil, California also refines some of its own oil, primarily drilled from Kern County. With the busiest port in the country (Los Angeles), California plays a pivotal role in the global supply chain, hauling in about 40% of goods imported to the US. Notable contributions to popular culture, ranging from entertainment, sports, music, and fashion, have their origins in California. Despite an exodus of filmmaking from California, Hollywood continues to be an important center of the U.S. film industry, one of the oldest and largest film industries in the world; profoundly influencing global entertainment since the 1920s. The San Francisco Bay Area's Silicon Valley is the center of the global technology industry.
The Spaniards gave the name Las Californias to the peninsula of Baja California (in modern-day Mexico). As Spanish explorers and settlers moved north and inland, the region known as "California", or "Las Californias", grew in both area and population. Eventually it included lands north of the peninsula, Alta California, part of which became the present-day U.S. state of California.
A 2017 state legislative document stated, "Numerous theories exist as to the origin and meaning of the word 'California'", and that all anyone knows is the name was added to a map by 1541 "presumably by a Spanish navigator".
The name is most likely derived from the mythical island of California in the fictional story of Queen Calafia, as recorded in a 1510 work The Adventures of Esplandián by Garci Rodríguez de Montalvo. Queen Calafia's kingdom was said to be a remote land rich in gold and pearls, inhabited by beautiful dark-skinned women who wore gold armor and lived like Amazons, and bred griffins for war.
Abbreviations of the state's name include CA, Cal, Calif, and US-CA.
California was one of the most culturally and linguistically diverse areas in pre-Columbian North America. Historians generally agree that there were at least 300,000 people living in California prior to European colonization. The Indigenous peoples of California included more than 70 distinct ethnic groups, inhabiting environments ranging from mountains and deserts to islands and redwood forests.
Living in these diverse geographic areas, the indigenous peoples developed complex forms of ecosystem management, including forest gardening to ensure the regular availability of important food sources and medicinal plants. This was a form of sustainable agriculture. To mitigate destructive large wildfires from ravaging the natural environment, indigenous peoples developed a practice of controlled burning. This practice was recognized for its benefits by the California government in 2022.
These groups were also diverse in their political organization, with bands, tribes, villages, and, on the resource-rich coasts, large chiefdoms, such as the Chumash, Pomo and Salinan. Trade, intermarriage, craft specialists, and military alliances fostered social and economic relationships between many groups. Although nations would sometimes war, most armed conflicts were between groups of men for vengeance. Acquiring territory was not usually the purpose of these small-scale battles.
Men and women generally had different roles in society. Women were often responsible for weaving, harvesting, processing, and preparing food, while men for hunting and other forms of physical labor. Most societies also had roles for people whom the Spanish referred to as joyas, who they saw as "men who dressed as women". Joyas were responsible for death, burial, and mourning rituals, and they performed women's social roles. Indigenous societies had terms such as two-spirit to refer to them. The Chumash referred to them as 'aqi. The early Spanish settlers detested and sought to eliminate them.
The first Europeans to explore the coast of California were the members of a Spanish maritime expedition led by Portuguese captain Juan Rodríguez Cabrillo in 1542. Cabrillo was commissioned by Antonio de Mendoza, the Viceroy of New Spain, to lead an expedition up the Pacific coast in search of trade opportunities; they entered San Diego Bay on September 28, 1542, and reached at least as far north as San Miguel Island. Privateer and explorer Francis Drake explored and claimed an undefined portion of the California coast in 1579, landing north of the future city of San Francisco. The first documented Asians to set foot on what is now the United States occurred in 1587, when Filipino sailors arrived in Spanish ships at Morro Bay. Descendants of the Islamic Caliph Hasan ibn Ali, who had been living in formerly Muslim Manila, transited through California while traveling to Guerrero, Mexico. These individuals, who had converted to Christianity while retaining some Islamic traditions, later played a role in Mexico's wars of independence. Sebastián Vizcaíno explored and mapped the coast of California in 1602 for New Spain, putting ashore in Monterey. Despite the on-the-ground explorations of California in the 16th century, Rodríguez's idea of California as an island persisted. Such depictions appeared on many European maps well into the 18th century.
The Portolá expedition of 1769–70 was a pivotal event in the Spanish colonization of California, resulting in the establishment of numerous missions, presidios, and pueblos. The military and civil contingent of the expedition was led by Gaspar de Portolá, who traveled over land from Sonora into California, while the religious component was headed by Junípero Serra, who came by sea from Baja California. In 1769, Portolá and Serra established Mission San Diego de Alcalá and the Presidio of San Diego, the first religious and military settlements founded by the Spanish in California. By the end of the expedition in 1770, they would establish the Presidio of Monterey and Mission San Carlos Borromeo de Carmelo on Monterey Bay.