The Mexican-American War of 1846 to 1848.
California was part of the northern portion of Mexico that was added to the US as a result of the Mexican-American War.
N+10
It added California and the Southwest.
california
California was added to the United States just before the US Civil War and allied with the Union side.
Date of admissionSept. 9, 1850
because they created a war over how much the money was
James K. Polk
Mexican-American War
The Mexican-American war
California was added to the United States on September 9, 1850. This made the state the 39th in the US.
People born in US territories become citizens of the US. When the US western border stretched from the Mississippi River to the California coast, new Americans born in those territories added to the "citizen population".