Why did Mexico sell California after the Mexican-American War?

There's a longer, more nuanced explanation, but it really comes down to this: Because they were forced to after the US invasion. read more

Mexico did NOT sell any territory in 1847. It was occupied and then taken away by the US after Mexico lost the war. To say that Mexico “ceded” it is an euphemism. By the way, the USA was also demanding Baja California and other states like Sonora, but Mexican diplomats saved them. read more

As a result, New Mexico was dependent on the overland Santa Fe Trail trade with the United States at the outbreak of the Mexican–American War. Mexico's military and diplomatic capabilities declined after it attained independence and left the northern half of the country vulnerable to the Comanche, Apache, and Navajo. read more