California Admission Day in the United States Date in the current year: September 9, 2024

The United States was originally composed of thirteen former British colonies that declared independence from the United Kingdom: Connecticut, Delaware, Georgia, Maryland, Massachusetts, New Jersey, New Hampshire, New York, Pennsylvania, North Carolina, Rhode Island, South Carolina, Virginia. These were the first U. S. states.

The rest of the states were admitted into the Union based on Article Four of the U. S. Constitution, which empowers the Congress to admit new states on an equal footing. Some of the states split from already existing ones (Tennessee from North Carolina, West Virginia and Kentucky from Virginia, Vermont from New York, Maine from Massachusetts), and some lay beyond the original thirteen colonies.

For example, California was a Spanish colony at the time when the U. S. Constitution was signed. The province of Alta California of New Spain included what is now California, Nevada and Utah, as well as parts of present-day Arizona, Colorado, New Mexico and Wyoming.

Following Mexico’s independence from Spain in 1821, Alta California became a remote and sparely populated territory of Mexico. In 1846, a group of American immigrants who lived in Alta California without an official permission declared the California Republic in the area around Sonoma. They controlled the territory for 25 days before joining the United States in the Mexican—American War.

The war ended in February 1848 with the signing of the Treaty of Guadalupe Hidalgo. According to the treaty, the United States gained Alta California and Santa Fe de Nuevo México, which corresponded to some or all of present-day Arizona, California, Colorado, Kansas, Nevada, New Mexico, Oklahoma, Texas, Utah, and Wyoming.

Initially, the U. S. federal government was in no hurry to divide the territory conquered from Mexico into states and incorporate them into the Union. However, the influx of immigrants caused by the California Gold Rush gave rise to the necessity of organizing the territory with its own local government, law enforcement, judicial system, etc.

The Constitution of California was adopted at the California Constitutional Convention in Monterey on November 13, 1849. Three months later, California applied to the Congress for admission to statehood. Following a fierce debate stemming from disagreements between slave and free states, the Congress passed the Compromise of 1850, which made it possible to admit California into the Union as a free state.

On September 7, 1850, the House of Representatives approved An Act for the Admission of the State of California. President Millard Fillmore signed it into law two days later, officially making California the thirty-first state. The anniversary of this event is celebrated as a legal day of observance entitled California Admission Day.