The premise of the Mexican-American was a territory dispute between the two states. In 1845, Texas became one of the American states, and the countries did not agree on the point where the territory of Texas was. The Mexicans claimed that Texas’s borders were at the Nueces River, while Americans stressed that the state’s boundaries were at the Rio Grande.
However, the major cause of the conflict was Americans’ sentiment to create a country that would spread all over the territory of the continent. After almost two years of war Mexico and the USA made peace. The major outcomes of the war were Mexico’s loss of territories and American expansion to California, New Mexico, Utah, Arizona, and Nevada. These new acquisitions had a considerable influence on the development of American society as they enhanced the pressure related to the slavery issue.