Are Arizona, New Mexico, Oklahoma & Texas a Formal Region?

No. These four states are not collectively designated as a formal region in any official geographic, administrative, or statistical framework.

How They're Actually Grouped

Informal Groupings That Include Some

• Southwest: AZ, NM (+ sometimes S. CO, S. UT, S. NV, W. TX)
• South Central: TX, OK, AR, LA
• Sun Belt: All 4 + CA, NV, UT, CO, etc.
• "Four Corners" states: AZ, NM, CO, UT (OK, TX not included)

Why the Confusion?

• All four were acquired in 19th-century expansion (Mexican Cession 1848, Texas Annexation 1845, Oklahoma Territory 1890)
• Share some arid/semi-arid climate, ranching history, Native American presence
• But Oklahoma & Texas have distinct Southern/Plains identities; Arizona & New Mexico are core Southwest

Bottom line: They're four distinct states in different census divisions, time zones, and cultural spheres — not a recognized region.