National California Day Date in the current year: February 22, 2025

California is a state in the Western United States, located on the Pacific Coast and bordered by Oregon, Nevada, Arizona, and the Mexican state of Baja California. Nicknamed the Golden State, it is the most populous state in the U.S. and the third-largest by area.

Prior to European colonization, California was one of the most culturally and linguistically diverse areas in North America, inhabited by more than 70 distinct indigenous ethnic groups with varying customs, traditions, and political organization. The first Europeans to set foot in California were members of a Spanish expedition led by Portuguese captain Juan Rodríguez Cabrillo in 1542.

By the time the Thirteen Colonies gained independence from the United Kingdom, California was part of New Spain. The Spanish province of Alta California encompassed present-day California, Nevada, and Utah, as well as parts of Arizona, Colorado, New Mexico, and Wyoming.

After Mexico gained independence from Spain in 1821, Alta California became a remote and sparsely populated Mexican territory. In 1846, a group of unauthorized American immigrants living in the Sonoma area declared the California Republic. Their control of the territory they claimed lasted only 25 days before they allied themselves with the United States in the Mexican-American War.

The war concluded in February 1848 with the Treaty of Guadalupe Hidalgo, by which the U.S. acquired Alta California and Santa Fe de Nuevo México—territories that now comprise all or parts of Arizona, California, Colorado, Kansas, Nevada, New Mexico, Oklahoma, Texas, Utah, and Wyoming.

At first, the U.S. federal government delayed dividing and incorporating the newly acquired land into the Union. However, the California Gold Rush triggered a massive influx of settlers, necessitating local governance, law enforcement, and a judicial system.

On November 13, 1849, the California Constitutional Convention in Monterey adopted the state’s first constitution. Three months later, California applied for statehood. Intense congressional debates followed, driven by conflicts between free and slave states. Finally, the Compromise of 1850 paved the way for California’s admission to the Union as a free state.

On September 7, 1850, the House of Representatives approved California’s statehood. President Millard Fillmore signed it into law two days later, officially making California the thirty-first state of the United States.

National California Day was created in 2017 as part of National Day Calendar’s National State Days project, which celebrates one state per week in the order of their admission to the Union. In this cycle, which begins on July 13 with National Delaware Day, National California Day falls on February 22. It should not be confused with California Admission Day, which is celebrated on September 9 to commemorate the anniversary of California’s admission to the Union.