What present USA States were part of Mexico in the past?

Answer 1

The whole states of California, Nevada, Utah, Arizona, New Mexico and Texas, as well as parts of Wyoming, Colorado, Oklahoma and Kansas.

The original US-Mexico border was defined by the Sabine River north from the Gulf of Mexico to the 32nd parallel north (32°N), then due north to the Red River, west along the Red River to the 100th meridian west (100°W), due north to the Arkansas River, west to its headwaters, north to the 42nd parallel north (42°N), and finally west along that parallel to the Pacific Ocean.

Texas was lost during the Texas Revolution (1835-1836). Territory of Texas at the time included present-day Texas, as well as those parts of Oklahoma, Kansas, Colorado and Wyoming described above.

During the Mexican-American War (1846-1848) Mexico lost all the remaining territories, including present-day California, Nevada, Utah and the rest of Colorado as well as most of northern New Mexico and Arizona. Also at the end of the war Mexico was forced to cease any attempt on reclaiming Texas. This is also known as the Mexican Cession (1848).

Finally, during the Gadsden Purchase (1853), Mexico sold parts of southern Arizona and New Mexico to the United States. This was the only peaceful purchase of land made from Mexico.