The Treaty of Guadalupe Hidalgo was a controversial treaty that ended the Mexican-American War. It is seen as a treaty largely imposed by the United States on Mexico rather than a negotiated settlement between the two warring nations. The treaty contained terms for the purchase of large swaths of formerly Mexican territory, but the arranged price for these lands was very small. This large acquisition of new land from the Treaty of Guadalupe Hidalgo strongly influenced U.S. historical events leading up to the American Civil War.
A number of settlers from the southern U.S. began immigrating to the area of modern-day Texas in the 1820s. These settlers generally identified more with the U.S. than with Mexico, which governed the region. Gradually, the immigrants became a majority, grew disillusioned with Mexican rule, and declared the independence of the Republic of Texas. After about six months of fighting, the Republic of Texas remained independent for ten years until it was annexed by the U.S. in 1846.
The Mexican government never recognized the independence of Texas and viewed its annexation by the U.S. as an act of war. President James Polk’s offer to purchase Mexican territories, including the Rio Grande border region of Texas, further angered Mexico. Finally, a U.S. military presence in the contested border region between the two countries resulted in a Mexican attack against those forces. The hostilities evolved into the full-scale Mexican-American War shortly thereafter.
Within two years, the U.S, had occupied the Mexican capital of Mexico City as well as Mexican territories stretching west to California. Many historians claim that the conduct of American military operations demonstrates the expansionist objectives of U.S. leaders of the time. In Mexico, the war is known as the North American Intervention in Mexico.
The Treaty of Guadalupe Hidalgo was signed in Mexico City on 2 February 1848. It stipulated that 1.36 million square kilometers (525,098 square miles) would be ceded to the U.S. in exchange for $15 million US Dollars (USD) (equal to $380 million USD today). This transfer of land is known as the Mexican Cession. Territories included the present U.S. states of California, Nevada, and Utah, and large parts of Arizona, New Mexico, and Colorado. The U.S. also agreed to take over debts worth $81.4 million USD today.
The amount of money paid to Mexico as part of the Treaty of Guadalupe Hidalgo was about half of what the U.S. offered years before for the land. Moreover, the U.S. paid Mexico $10 million USD for a much smaller piece of land in the 1854 Gadsden Purchase. The peacetime Gadsden Purchase involved only about 6% of the amount of land acquired from the Treaty of Guadalupe Hidalgo; the U.S., however, was willing to pay more than half the amount it paid for the Mexican Cession.