That year, the Treaty of Guadeloupe. Under the terms of the treaty negotiated by Trist, Mexico ceded Alta California and New Mexico to the United States. This was known as the Mexican Cession and included current Arizona and New Mexico and parts of Utah, Nevada and Colorado (see Article V of the treaty). Mexico also waived all claims to Texas and recognized the Rio Grande as the southern boundary with the United States (see Article V).
Many cities and towns in California originated as Catholic missions established by the Spanish government to spread their faith in the New World. On the map above, the borders of the state of California were much smaller than the territory acquired from California. By then, California was home to a native population now reduced to less than 100,000 and another 14,000 permanent residents. When British, Canadian and American settlers moved to Oregon, there was also an inevitable invasion of non-Mexicans into Northern California across that border.
Under its terms, Mexico ceded 55 percent of its territory, including the current states of California, Nevada, Utah, New Mexico, most of Arizona and Colorado, and parts of Oklahoma, Kansas and Wyoming. Not only were Californians allowed to trade with foreigners, but foreigners could also own land in the province once they had naturalized and converted to Catholicism. Known as the bear flag revolt, this insurrection represented one of the first aggressive actions that divided California from Mexico. Many of today's California cities were established and named, including San Diego, Los Angeles, and San Francisco.
A new era began in California when ranch life flourished and American trappers began to enter the territory. In San Diego, Serra founded the first of 21 Spanish missions that extend along the California coast. With the expedition was Father Junipero Serra, a Franciscan father who would have a tremendous influence on the colonization of California through the establishment of missions. The first organized group of settlers from the United States to cross the plains into California was the party led by John Bidwell and John Bartleson in 1841.Many ignorant people tell immigrants, especially Mexicans, to “return to their country, when states like Texas, Arizona and California actually once their country.
On March 10, 1848, the Senate approved a treaty that led California and much of the Southwest to join the United States. California's vast natural resources and thriving population led to the desire to incorporate the territory of California into the United States as a state. In 1821, Mexico achieved independence, and news of this event reached Alta California the following year.