Soon after the outbreak of war in 1846, United States forces invaded the Mexican province of Alta California. Seven months later, on Jan. 13, 1847, representatives of both countries signed the Treaty of Cahuenga in the San Fernando Valley, ending the fighting.

For three years, California remained under American martial law. During this period, gold was discovered and its population exploded, which gave impetus to the demand that California be admitted to the Union. In 1849, leaders from around the future state met in Monterey to draft the first constitution, which was approved on Nov. 13 by a vote of 12,064 to 811. Peter Burnett was elected governor, and in January 1850, the state Legislature began its first session.

As California lawmakers began establishing the basic institutions of state governance, the U.S. Congress argued about whether to admit California to the Union as a slave or free state or as two separate states, one slave and one free. The issue was resolved by the famous Compromise of 1850, and on Sept. 9 of that year California was admitted as the 31st state.

California’s early history is too often neglected in schools and among our citizens. For that reason, Gov. Jerry Brown called upon Californians to pause and celebrate Admission Day this year by reflecting on how it was that California became the 31st state.