The Treaty of Guadalupe Hidalgo was signed on February 2, 1848. This treaty was officially the terms of surrender by Mexico. The war this treaty ended-unofficially known as “Mr. Polk’s War”-began on May 13, 1846.
On that date, Congress-at President Polk’s bidding-declared war on Mexico after sixteen American soldiers under General Zachary Taylor were killed along the border of Texas, which had become a state in 1845.
The terms of the treaty allowed the U.S. to add nearly 2 million square miles to its borders, including what is now California, Arizona, Nevada, Utah, New Mexico, and parts of Colorado and Wyoming. President Polk led this expansionist fervor known as Manifest Destiny.