Southwestern United States The Southwestern United States (also
known as the American Southwest or simply the Southwest) is a
region defined in different ways by different sources. Broad
definitions include nearly a quarter of the United States,
including Arizona, California, Colorado, Nevada, New Mexico,
Oklahoma, Texas and Utah. Narrowly defined, the "core" Southwest
is centered around the Four Corner states, with parts of the
other states making up the beginnings and endings of the
Southwest. The five main southwestern states; Arizona, New
Mexico, Colorado, Utah, and Nevada are also all considered part
of the Mountain West, as well as the southwest. The total
population of these states is roughly 19 million people. Most of
it was a part of the Viceroyalty of New Spain, in the Spanish
Empire, during the Modern Era. What is now California, Arizona,
Nevada, Utah, New Mexico, and portions of Colorado, Wyoming,
Oklahoma and Kansas were part of Mexico before the Mexican-
American War and the Gadsden Purchase of 1