Settlers went into conflict with the Mexican government because they were planters who brought slaves. Mexico had abolished slavery before and refused this practice. Texas later became independent shortly and joined the USA in 1845.
A border dispute over whether Texas ended at the Nueces River (Mexican claim) of the Rio Grande (U.S. claim)
An attack on American troops by Mexican soldiers in the disputed area between the two rivers on April 25, 1846.
The Unites States annexation of Texas in 1845
General Zachary Taylor, a hero of the war, used his newfound notoriety to become the twelfth president of the U.S.
Mexico ceded to the United States nearly all of the territory now included in the states of New Mexico, Utah, Nevada, Arizona, California, Texas, and western Colorado in exchange for $15 million
The reopening of the slavery-extension issue, which had been largely dominant since the Missouri Compromise of 1820, and a corresponding rise in sectional antagonism in the U.S.