Answer:
The US mainland boundary to Mexico from 1848-1853: Texas, New Mexico, Arizona, Utah and California.
Explanation:
Territorial Evolution in US mainland Border States.
1846 - Texas was annexed by the Federal Government after a Local Referendum, and approved by the US Congress.
1846- The Northwest part of California starts to be American Territory.
1848 - The Guadalupe Hidalgo Treaty formalized the cession over territories such as (the greater part of California), (Northern part of ) New Mexico. Colorado, Utah, Nevada, and Arizona. By the end of the Mexican American War.
1853- The Gadsden Purchase was the final act to buy the southern part of New Mexico.
