Mexican Territory in 1848: What Remained After the Mexican-American War?

The Treaty of Guadalupe Hidalgo (1848) ended the Mexican-American War, forcing Mexico to cede **~55% of its pre-war territory** to the United States.

Territory Lost (Mexican Cession)

Mexico surrendered all claims to:

• Alta California (modern CA, NV, UT, parts of AZ, WY, CO)
• Nuevo México (modern NM, parts of AZ, CO, TX)
• Disputed Texas territory (Rio Grande boundary confirmed)

Total: **~2.5 million km²** — now the US Southwest.

Territory Retained by Mexico (1848)

Mexico kept the **southern core**:

• All of modern **Mexico** (31 states + Federal District)
• **Baja California** peninsula
• **Yucatán** peninsula
• **Chiapas, Oaxaca, Guerrero, Veracruz, Puebla, etc.**

Essentially, **everything south of the new border** (Gila River → Rio Grande line).

Later Loss

The **Gadsden Purchase (1854)** transferred southern Arizona/southwestern New Mexico (76,800 km²) to the US for $10M—the final border adjustment.

Key Takeaway

In 1848, Mexico controlled **only its current territory minus the Gadsden strip**. The northern half (today's US Southwest) was lost.