California became a U.S. state on September 9, 1850, when it was admitted to the Union as the 31st state.

Quick Scoop

  • Statehood date: September 9, 1850.
  • State number: California entered as the 31st state in the Union.
  • Context: Its admission came as part of the Compromise of 1850 and it joined as a free (non-slave) state.

In simple terms: California switched from a rapidly growing frontier region to a full-fledged U.S. state on September 9, 1850.

TL;DR: When did California become a state? → September 9, 1850. ✅

Information gathered from public forums or data available on the internet and portrayed here.