- In 1821, Mexico won its independence from Spain and established a federal republic.
- In 1836, Texas declared independence from Mexico and became a republic.
- In 1845, the United States annexed Texas, which Mexico considered an act of war.
Disputed Border
- The border between the United States and Mexico was not clearly defined.
- The United States claimed the Rio Grande as the border, while Mexico claimed the Nueces River.
- This dispute led to conflicts between American settlers and Mexican ranchers.
Manifest Destiny
- Manifest Destiny was the belief that it was the United States' destiny to expand across the North American continent.
- Manifest Destiny motivated many Americans to support the annexation of Texas and the war with Mexico.
