Question: When did california become a state of the united states?

Disambiguated questions and answers:
context: What is now California was first settled by various Native Californian tribes before being explored by a number of European expeditions during the 16th and 17th centuries. The Spanish Empire then claimed and conquered it. In 1804 it was included in Alta California province, within Spanish New Spain Viceroyalty. The area became a part of Mexico in 1821 following its successful war for independence but was ceded to the United States in 1848 after the Mexican–American War. The western portion of Alta California was then organized and admitted as the 31st state on September 9, 1850. The California Gold Rush starting in 1848 led to dramatic social and demographic changes, with large-scale emigration from the east and abroad with an accompanying economic boom.
question: When did the land that is California become part of the united States?
short_answers: 1848
wikipage: California

context: Once the state's Constitutional Convention had finalized its state constitution, it applied to the US Congress for admission to statehood. On September 9, 1850, as part of the Compromise of 1850, California was officially admitted into the United States as an undivided free state. Its status as a 'free state' prevented the expansion of slavery to the Pacific Coast, which was a foremost concern for the pre-Civil War US Congress. Within the state of California, Sep 9 remains as an annually celebrated legal holiday known as California Admission Day.
question: When was California officially added to the United States?
short_answers: September 9, 1850
wikipage: California

Long answers:
knowledge: content: The western portion of Alta California was then organized and admitted as the 31st state on September 9, 1850, following the Compromise of 1850.
wikipage: California

content: The area became a part of Mexico in 1821, following its successful war for independence, but was ceded to the United States in 1848 after the Mexican–American War.
wikipage: California

content: What is now California was first settled by various Native Californian tribes before being explored by a number of Europeans during the 16th and 17th centuries.
wikipage: California

content: California is a state in the Western United States. It is bordered by Nevada to the east, Arizona to the southeast, the Pacific Ocean to the west, Oregon to the north, and the Mexican state of Baja California to the south. With over 39.5 million residents across a total area of approximately 163,696 square miles (423,970 km2), it is the most populous and the third-largest U.S. state by area.
wikipage: California
long_answer: California is the most populous and third largest state in the Western United States, which is bordered by Nevada to the east, Arizona to the southeast, the Pacific Ocean to the west, Oregon to the north, and the Mexican state of Baja California to the south. The area that is now California was first settled by various Native Californian tribes before being explored by a number of Europeans during the 16th and 17th centuries. It became a part of Mexico in 1821, following its successful war for independence, but was ceded to the United States in 1848 after the Mexican-American War. California was officially admitted to the United States as the 31st state on September 9, 1850.