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Mexico has passed the boundary of the United States, has invaded our territory and shed American blood upon the American soil. She has proclaimed that hostilities have commenced, and that the two nations are now at war. War Message to Congress

War Message to Congress

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Legacy

The land of the U.S. grew by more than one million square miles under Polk’s administration. Guiding the president’s efforts was a belief known as “Manifest Destiny,” the conviction that the U.S. was entitled to rule as much of the continent as it could acquire. The tremendous expansion was not without controversy, however, and many American citizens were divided about the friction and potential war with both Great Britain and Mexico that would be necessary to gain this land. One dispute lay with Britain over the Oregon boundary. The U.S. was claiming land in the Pacific Northwest region as far north as Alaska, but the British were claiming land as far south as Portland. Because the British were not eager to fight, Polk was able to negotiate a treaty for what is now Oregon and Washington in 1846.

The second dispute lay with Mexico. Texas had been annexed by President Tyler in 1845, but Mexico challenged the border. In addition, Polk was interested in California and New Mexico, but Mexico was unwilling to negotiate. Polk sent General Zachary Taylor and the Army to the disputed area on Texas’s western border. Mexico perceived this as an act of aggression and attacked. Congress declared war, and after sixteen months of American successes, the U.S. captured Mexico City. Finally, the U.S. and Mexico negotiated the Treaty of Guadalupe Hidalgo, in which the U.S. paid $15 million and Mexico ceded a Rio Grande border for Texas, as well as what is now California, Nevada, and Utah plus much of New Mexico, Arizona, Wyoming, and Colorado.