The state of Texas is associated with three regions in the United States: Southern, Southwestern and the Old Southwest. The most encompassing region among the three is Southern states, which describes states that are south of the Mason-Dixon Line and the Ohio River.
The Southwestern region is made up of southern states that are located west of the Mississippi River, which includes Arkansas, Arizona, California, Colorado, Louisiana, Nevada, New Mexico, Oklahoma, Texas and Utah. The Old Southwest region refers to states located in the Southwest prior to Mexico giving up land during the Mexican War. This region is made up of Arkansas, Kentucky, Louisiana, Missouri, Tennessee and Texas.