Gulf Coastal Plains region map
One of the 4 natural regions · sea level to ~1,000 ft · about two-fifths of Texas · Central Time
The Gulf Coastal Plains is the largest of the four natural regions of Texas and the one most Texans live in. It takes in everything east and south of the Balcones Escarpment: pine forest in the northeast, black prairie down the middle, marsh and rice fields along the coast, and thorn brush to the Rio Grande. Houston, San Antonio, Dallas and Austin all sit inside it.
The region runs from the Red River and the Sabine southwest to Brownsville. Its inland edge is the line of hills behind San Antonio, San Marcos and Austin.
Where it starts and ends
The western boundary is the Balcones Escarpment, a fault zone rather than a river or a road. Land on the west side was lifted a few hundred feet; land on the east side dropped and was buried in younger sediment. The line begins at Del Rio on the Rio Grande, runs northeast through Uvalde and along the northern edge of San Antonio, then bends north through New Braunfels, San Marcos and Austin and fades out north of Waco. I-35 follows the foot of it, which is why those cities are strung out in a line: each grew at a spring where water from the plateau reaches the surface. Comal Springs at New Braunfels, San Marcos Springs and Barton Springs in Austin are all on the fault.
North of Waco the boundary is harder to see on the ground. There it runs along the Eastern Cross Timbers, a narrow belt of sandy oak woods through Denton and Arlington: Dallas, built on black prairie clay, is in the Gulf Coastal Plains, while Fort Worth, 30 miles west on limestone, is in the Interior Lowlands. Everything east and south of that line — to the Sabine, the Gulf and the Rio Grande — belongs to this region.
The five belts
| Belt | Ground | Rain | What is grown |
|---|---|---|---|
| Piney Woods | Rolling sand and sandy loam over clay; loblolly and shortleaf pine | 40–55 in | Commercial timber, poultry, cattle |
| Post Oak Belt | Sandy loam savannah between the pines and the prairie | 35–45 in | Cattle, hay, some cotton and sorghum |
| Blackland Prairie | Deep dark calcareous clay that swells and cracks | 30–45 in | Corn, sorghum, wheat, cotton — and most of the region's cities |
| Gulf Prairies and Marshes | Flat clay, bays, barrier islands and salt marsh | 30–56 in | Rice, cotton, sorghum, cattle, sugarcane and citrus in the delta |
| South Texas Plain | Sandy and caliche soils under mesquite, blackbrush and prickly pear | 20–30 in | Cattle, winter vegetables, onions, grain |
Rainfall drops by roughly an inch for every 15 miles you drive west: more than 55 inches a year at Orange on the Louisiana line, close to 20 at Laredo.
Counties in the region
| Belt | Counties |
|---|---|
| Piney Woods | Bowie, Cass, Harrison, Panola, Shelby, Nacogdoches, Rusk, Gregg, Smith, Cherokee, Angelina, Polk, Tyler, Jasper, Newton, Hardin, Montgomery, Walker |
| Post Oak Belt | Bastrop, Lee, Burleson, Milam, Brazos, Grimes, Leon, Freestone, Anderson, Henderson, Fayette, Washington |
| Blackland Prairie | Dallas, Collin, Grayson, Fannin, Hunt, Kaufman, Ellis, Navarro, Hill, McLennan, Falls, Bell, Williamson, Travis, Hays, Caldwell, Guadalupe, Bexar |
| Gulf Prairies and Marshes | Orange, Jefferson, Chambers, Harris, Galveston, Brazoria, Fort Bend, Wharton, Matagorda, Jackson, Calhoun, Victoria, Refugio, Aransas, Nueces, Kleberg, Willacy, Cameron |
| South Texas Plain | Webb, Zapata, Starr, Hidalgo, Brooks, Duval, Jim Wells, McMullen, La Salle, Dimmit, Zavala, Frio, Atascosa, Karnes, Goliad, DeWitt, Wilson, Maverick |
Counties on the western edge — Bexar, Travis, Hays, Uvalde, Bell — are split by the escarpment and appear on both this map and the Great Plains one.
Cities
- Houston
2,304,580 people (2020), built on coastal prairie clay 50 miles inland from the Gulf and connected to it by the Houston Ship Channel.
- San Antonio
1,434,625 people. Downtown sits at the foot of the escarpment beside the San Antonio River springs; the north side climbs onto the plateau.
- Dallas
1,304,379 people, on the Blackland Prairie at a Trinity River ford — the black clay is why the area grew as a cotton market.
- Austin
961,855 people, straddling the Balcones fault: hills and limestone west of MoPac, prairie east of I-35.
- Corpus Christi
317,863 people on the Coastal Bend, with the deepwater port and refineries on the ship channel.
- Beaumont
115,282 people in the wettest corner of Texas, next to Spindletop and the Sabine–Neches refining strip.
- McAllen
142,210 people in the Rio Grande delta, the citrus, sugarcane and winter-vegetable country of the Rio Grande Valley.
- Tyler
105,995 people in the Piney Woods, above the East Texas Oil Field and the sandy soils that made it a rose-growing center.
What is farmed and what is drilled
The Blackland Prairie has the best cropland in the state: a dark, lime-rich clay two to four feet deep that grows corn, grain sorghum, wheat and cotton, and that shrinks and cracks so badly in drought it breaks foundations. It was the cotton belt before mechanization, and it is now mostly the I-35 and I-45 urban corridor. On the coastal prairie southwest of Houston — Wharton, Matagorda, Jackson and Colorado counties — the clay holds water well enough for flooded rice. In the delta below Harlingen the frost-free season is long enough for grapefruit, oranges, sugarcane and winter onions. The Winter Garden counties of Zavala, Dimmit and Frio irrigate spinach, onions and carrots from the Carrizo aquifer. In the Piney Woods, pine plantations are harvested on a 25 to 35 year cycle for lumber and paper.
The Texas oil industry began in this region. The Lucas gusher at Spindletop, just south of Beaumont, blew in on January 10, 1901. The East Texas Oil Field, found near Kilgore in Gregg and Rusk counties in 1930, was the largest field in the lower 48 for decades. Since 2008 the Eagle Ford Shale has been drilled along an arc from Webb County through La Salle, Karnes and DeWitt. The refineries that process it stand at Port Arthur, Texas City, Baytown and Corpus Christi.
Distinctive facts
| Share of the state | Roughly two-fifths of the land area of Texas and a large majority of its people |
| Highest ground | About 1,000 ft along the Balcones Escarpment; the rest slopes to sea level |
| Wettest place | The Sabine corner around Orange and Newton, over 55 inches a year |
| Coastline | About 367 miles of Gulf shoreline behind a chain of barrier islands |
| Biggest county | Harris, 4,731,145 people in 2020 |
| First oil | Spindletop, Jefferson County, 1901 |