4 regions of Texas map
Sheet TX-07 · 4 physiographic regions · boundaries: Balcones Escarpment · Caprock Escarpment · Pecos River
The four regions taught in Texas schools are landform regions, not cultural ones. They are the Texas ends of four provinces that continue into other states: the Gulf Coastal Plain running to Florida, the Central Lowland of the Midwest, the Great Plains that reach Canada, and the Basin and Range country of the Southwest. Each boundary is a real physical feature you can see from a road.
The regions are not drawn on the base map. Use the boundary landmarks in the table to place them: the Balcones Escarpment runs roughly along I-35 from Del Rio to Waco, and the Caprock Escarpment runs north–south just east of Lubbock and Amarillo.
The four regions compared
| Region | Share of Texas | Boundary landmark | Cities |
|---|---|---|---|
| Gulf Coastal Plains | about one third | Bounded inland by the Balcones Escarpment and Fault Zone; the Gulf shoreline on the other side | Houston, San Antonio, Corpus Christi, Brownsville, Beaumont, Laredo |
| Interior Lowlands | about one fifth | Balcones Escarpment on the southeast, Caprock Escarpment on the west | Fort Worth, Wichita Falls, Abilene |
| Great Plains | about one quarter | Caprock Escarpment on the east, Pecos River on the west, Balcones Escarpment on the south | Lubbock, Amarillo, Midland, Odessa, San Angelo, Kerrville |
| Basin and Range | about one tenth | Everything west of the Pecos River, to the Rio Grande and the New Mexico line | El Paso, Alpine, Marfa |
Shares are approximate. Different sources draw the Interior Lowlands–Great Plains line and the southern edge of the Edwards Plateau in slightly different places, which moves the percentages by several points.
What separates them on the ground
The Balcones Escarpment is the sharpest line in the state. It is a fault zone where the land drops several hundred feet from the Edwards Plateau to the coastal plain, and the drop is why Austin's west side is hilly and its east side is flat, why San Antonio has springs along its northern edge, and why I-35 follows the base of it from Del Rio through San Antonio, Austin and Waco. Everything southeast of that line is Gulf Coastal Plains; everything northwest of it is Great Plains or Interior Lowlands.
The Caprock Escarpment does the same job 300 miles further northwest. It is the eastern rim of the Llano Estacado, a wall of 200 to 1,000 feet that separates the flat High Plains from the Rolling Plains below. US-84 climbs it at Post, I-27 runs on top of it, and Palo Duro Canyon is cut into it. West of the High Plains the third boundary is the Pecos River, which marks the start of the Trans-Pecos and the only part of Texas with true mountains.
The fourth edge is the coast itself. The Gulf Coastal Plains do not stop at the beach: they continue offshore as the continental shelf, and the barrier islands from Galveston to South Padre are the newest part of the region.
Sub-regions inside each
| Region | Sub-regions | What you see there |
|---|---|---|
| Gulf Coastal Plains | Piney Woods, Post Oak Belt, Blackland Prairie, Coastal Prairies and Marshes, South Texas Plain | Pine forest in the east, black clay farmland through Dallas and Waco, rice and marsh near the coast, thorny brush country toward Laredo |
| Interior Lowlands | Grand Prairie, Eastern and Western Cross Timbers, Rolling Plains | Alternating oak belts and open prairie, then red-dirt ranch country toward the Red River |
| Great Plains | High Plains (Llano Estacado), Edwards Plateau, Llano Uplift | Dead-flat cotton and grain land above the Caprock; limestone hills and spring-fed rivers on the plateau; granite domes such as Enchanted Rock in the uplift |
| Basin and Range | Guadalupe, Davis and Chisos Mountains, Salt Basin, Big Bend | Desert flats between isolated mountain ranges, the only alpine terrain in Texas, and the deepest canyons on the Rio Grande |
How the regions change the numbers
Rainfall falls almost in a straight gradient from east to west across the four regions, from more than 50 inches a year in the Piney Woods corner of the Gulf Coastal Plains to under 10 inches in the Basin and Range. Elevation runs the other way: sea level on the coast, roughly 500 to 1,000 feet across the Interior Lowlands, 3,000 to 4,500 feet on the High Plains, and 8,751 feet at Guadalupe Peak, the state's high point, in the Basin and Range.
Population runs opposite to area. The Gulf Coastal Plains hold most of the state's people, including three of the five largest cities. The Basin and Range covers a tenth of Texas but, outside El Paso, contains counties measured in single-digit thousands of residents — Loving County, on its northern edge, recorded 64 people in 2020.