Mexican-American War (25 avr. 1846 – 2 févr. 1848)

Description:

The United States and Mexico went to war against each other in 1846 because the US said the border was at the Rio Grande river, while Mexico said it was at the Nueces river. When troops from both sides met at the Rio Grande, fighting broke out. The United States won the war and bought Texas and California from Mexico.
This increased sectionalism because Texas was added as a slave state and the US acquired more land out west to create new states.