American territorial ambitions in Texas and the Southwest were the underlying causes of the Mexican–American War, while Mexico resented the influx of American settlers, primarily in Texas, and their refusal to assimilate. By the end of the war, the United States had increased the previous area of the country by more than a third. Although the war was a victory for the United States, it would soon be overshadowed by the controversy over slavery in the territories acquired from Mexico.
United States
* Annexation of Texas
* Secure its annexation of Texas
* Acquisition of the Southwest: Texas, New Mexico, Arizona, Nevada, Utah, Colorado, and parts of Wyoming, Kansas, and Oklahoma.
Mexico
* Repel the American invasion of Texas
* Protect the rights of its citizens living in Texas and the acquired territories
* Obtain compensation for damages inflicted on Mexican citizens by American settlers in Texas