U.S.-Mexico Relations and Expansion

The United States declared war on Mexico in May 1846 after troops clashed near the Rio Grande River.

• Cause

• Effect

President Polk wanted to expand the United States and annexed Texas in 1845.

• Cause

• Effect

California requested admission as a free state, intensifying debates over slavery.

• Cause

• Effect

U.S. territory expanded from the Atlantic coast to the Pacific coast.

• Cause

• Effect

Mexico never recognized Texas independence and considered it a rebellious state.

• Cause

• Effect

The U.S. purchased the Gadsden territory from Mexico in 1854 for a southern railroad route.

• Cause

• Effect

Mexican troops crossed the Rio Grande River and engaged U.S. troops in the disputed area in 1846.

• Cause

• Effect

There was a disagreement between the U.S. and Mexico about whether the border of Texas was at the Nueces River or the Rio Grande.

• Cause

• Effect

The Treaty of Guadalupe Hidalgo (1848) ended the war and gave the U.S. territories including New Mexico, Arizona, California, and others (the Mexican Cession).

• Cause

• Effect

The United States claimed Mexico attacked first; Mexico claimed the U.S. provoked the war to gain Mexican territory.

• Cause

• Effect