Beginning in spring 1846, after various diplomatic, informal economic, and unofficial militaristic attempts to take and occupy part of Mexico’s northern frontier, the U.S. declared war on its southern neighbor. A decade after their politically unresolved dispute over Tejas, this war lasted for about one and a half years and resulted in the transfer of almost half of Mexico’s territory to the United States.
The Treaty of Guadalupe Hidalgo, signed on February 2, 1848 and ratified by both nations the subsequent spring, agreed to a payment of $15 million for the lost territory; settled the dispute over Texas in the favor of the United States; made stipulations about the land transfer; and detailed responsibilities and obligations regarding the actions of the Native Americans living on much of that land (many of whom never recognized a “foreign” power sovereignty over them and, accordingly, were hostile to Mexico and the United States). The Treaty also detailed what was to become of the Mexicans living in the newly conquered territories.
Mexicans in the now occupied lands were to be protected under the laws of the United States and the Treaty. They retained the right to their language, religion, and culture. Their property and land was protected by the law. As for citizenship, they were offered one of three options: 1) declare their intent to retain Mexican citizenship; 2) leave to Mexico; or 3) become U.S. citizens by declaration or by doing nothing.
This was the first time in U.S. history that citizenship was extended to a population that was not formally recognized as “white” by the federal government.
Two generations later, most Mexicans living in the U.S. no longer held title to their lands and found their cultural way of life increasingly under attack as U.S. white supremacy came to predominate. In California, as land transferred from Mexican to Euro-American hands, a very racially-motivated Workingman’s Party dominated the call for a Constitutional Convention. In 1879, that new Constitution not only made Chinese immigration illegal (the primary cause of the Party), but it also destroyed the legal protections Mexicans once enjoyed, rights promised to them in the 1848 Treaty. California once required Spanish and English as the languages of it official business. Now the new Constitution followed the already common practice of an English language state.
The “nation of laws” violated international and domestic laws in order to secure a democracy for some (white, European, male) at the expense of others (Mexican and nonwhite).
For more information, see:
• Racial Fault Lines: The Historical Origins of White Supremacy in California (Almaguer);
• Manifest Destinies: The Making of the Mexican American Race (Gomez); and
• Border Citizens: The Making of Indians, Mexicans, and Anglos in Arizona (Meeks)
For more details on life for Mexicans in California after the war, see the classic Decline of the Californios: A Social History of the Spanish-Speaking Californias, 1846-1890 (Pitts). The newer Negotiating Conquest: Gender and Power in California, 1770s to 1880s (Chavez-Garcia), which pays particular attention to issues of gender and sexuality, is also an excellent source.