Treaty of Guadalupe Hidalgo
The Mexican Cession (in red) was acquired through the Treaty of Guadalupe Hidalgo that ended the Mexican–American War. The Gadsden Purchase (in orange) was acquired through purchase after Polk left office.
The Mexican Cession acquired through the Treaty of Guadalupe Hidalgo included the entirety of California, Nevada, and Utah; the majority of Arizona; and portions of Wyoming, Colorado, and New Mexico. The Gadsden Purchase included southern Arizona and the southwest corner of New Mexico.
Source
Boundless vets and curates high-quality, openly licensed content from around the Internet. This particular resource used the following sources:
"James K. Polk."
http://en.wikipedia.org/wiki/James_K._Polk%23Presidency_.281845.E2.80.931849.29
Wikipedia
Public domain.