Treaty of Guadalupe Hidalgo — Mexico Cedes 55% of Territory to US

The Treaty of Guadalupe Hidalgo, signed February 2, 1848, ended the Mexican-American War. Mexico ceded 2.3 million km² — modern California, Nevada, Utah, most of Arizona and New Mexico, and parts of Colorado, Wyoming, Kansas, and Oklahoma — in exchange for $15 million ($525 million in 2024 dollars). The Rio Grande was established as the Texas border. Over 80,000 Mexicans who chose to remain in ceded territory became US citizens; their property rights were systematically violated in subsequent decades.