[Page 748]Most broadly, the southwest has been defined to include Texas, Oklahoma, Colorado, Utah, Nevada, New Mexico, and Arizona. Texas and Oklahoma, at least in the eastern half of each state, are predominately southern in culture, and so are sometimes treated as both southern and southwestern. At its core are the states of Arizona and New Mexico. To the east is the portion of Texas where Interstate Highway 35 runs from Laredo north into Kansas to include the western portion of Oklahoma. The northern portion of the southwest could include Nevada and Utah as well as southern Colorado.

The southwest has been defined several ways in the history of the United States. Prior to the Louisiana Purchase in 1803, the southwest was the current state of ...