Basin and Range region map
One of the 4 natural regions · 9 counties · 31,478 sq mi · 2,500 ft to 8,751 ft · Mountain & Central Time
The Basin and Range region is the smallest of the four natural regions of Texas and the only one with mountains. West of the Pecos River, block-faulted ranges rise a mile or more above flat desert basins, and every Texas peak higher than 5,280 feet stands in these nine counties.
From El Paso and the Guadalupe Mountains southeast to the Big Bend of the Rio Grande. The Pecos River closes the region off on the east.
Where it starts and ends
The eastern boundary is the Pecos River. It enters Texas from New Mexico at Red Bluff Reservoir on the Loving–Reeves line, runs southeast past Pecos, Girvin and Sheffield, and joins the Rio Grande in Amistad Reservoir above Del Rio. East of the river the land is the flat, oil-drilled tableland of the Great Plains; west of it, ranges start standing up out of the basins. Texans call the whole area the Trans-Pecos, and geologists call it the southeastern corner of the Basin and Range province that continues through New Mexico, Arizona and Nevada.
The other boundaries are political rather than physical. The Rio Grande makes the southern and western edge, with the Sierra Madre and the Chihuahuan Desert continuing on the Mexican side. New Mexico closes it off in the north. Nine counties are conventionally counted as Trans-Pecos: El Paso, Hudspeth, Culberson, Reeves, Jeff Davis, Presidio, Brewster, Pecos and Terrell. The last three straddle the river, so their eastern halves belong as much to the plains.
The nine counties
| County | Seat | Pop. 2020 | Sq mi |
|---|---|---|---|
| El Paso | El Paso | 865,657 | 1,015 |
| Pecos | Fort Stockton | 15,193 | 4,765 |
| Reeves | Pecos | 14,748 | 2,642 |
| Brewster | Alpine | 9,546 | 6,193 |
| Presidio | Marfa | 6,131 | 3,856 |
| Hudspeth | Sierra Blanca | 3,202 | 4,572 |
| Culberson | Van Horn | 2,188 | 3,812 |
| Jeff Davis | Fort Davis | 1,996 | 2,265 |
| Terrell | Sanderson | 760 | 2,358 |
Take El Paso County out and the remaining eight counties hold about 53,800 people spread over 30,500 square miles — roughly one person for every 360 acres. Brewster is the largest county in Texas.
The ranges
| Range | High point | County | Rock |
|---|---|---|---|
| Guadalupe Mountains | Guadalupe Peak, 8,751 ft — the highest in Texas; El Capitan, 8,085 ft | Culberson | Permian reef limestone |
| Davis Mountains | Mount Livermore, about 8,378 ft | Jeff Davis | Volcanic tuff and lava |
| Chisos Mountains | Emory Peak, 7,825 ft | Brewster | Volcanic and intrusive rock |
| Franklin Mountains | North Franklin Peak, 7,192 ft | El Paso | Faulted block inside the city limits |
| Chinati Mountains | Chinati Peak, above 7,700 ft | Presidio | Collapsed volcanic caldera |
| Eagle Mountains and Sierra Diablo | Eagle Peak, above 7,400 ft | Hudspeth | Fault blocks standing over the Salt Basin |
The Guadalupes are the exposed part of a fossil reef that grew in a Permian sea; the Davis and Chisos mountains are the wreckage of volcanoes. That is why one is gray and the other red.
Cities and towns
- El Paso
678,815 people (2020) in the far western corner, at the pass where the Rio Grande turns southeast. Larger than the rest of the region a dozen times over, and on Mountain Time.
- Alpine
6,035 people at 4,475 ft in Brewster County, on US-90 and the Union Pacific main line, with Sul Ross State University above town.
- Marfa
1,788 people on the Marfa Plateau, seat of Presidio County, a ranching town turned art town.
- Reeves County
Pecos, the seat, sits on I-20 in the irrigated valley the town's cantaloupes came from, now the center of Delaware Basin drilling.
- Pecos County
Fort Stockton, where I-10 and US-285 cross, grew around Comanche Springs and the 1859 army post.
- Culberson County
Van Horn is the I-10 stop at the foot of the mountains; the county reaches north to Guadalupe Peak.
- Jeff Davis County
Fort Davis, at about 5,050 ft, is one of the highest towns in Texas; McDonald Observatory stands on Mount Locke above it.
- Hudspeth County
Sierra Blanca and Dell City, split between I-10 and the irrigated farms of the Salt Basin.
Roads
- I-10 – the only interstate, running from El Paso through Van Horn and Fort Stockton; the Van Horn to Fort Stockton stretch is about 130 miles with an 80 mph limit.
- I-20 – splits off I-10 near Kent and heads east through Pecos toward Odessa.
- US-90 – the southern route through Marfa, Alpine, Marathon and Sanderson to Del Rio.
- US-62/180 – El Paso northeast past the Hueco Tanks and the Guadalupe Mountains to Carlsbad.
- US-67 – Marfa south to Presidio and the international bridge at Ojinaga.
- US-385 and SH-118 – the two roads into Big Bend National Park, from Marathon and from Alpine.
- SH-17 and SH-166 – the Davis Mountains loop through Fort Davis and the observatory.
Desert, water and what is drilled
This is the northern end of the Chihuahuan Desert: creosote bush, lechuguilla, ocotillo and sotol on the basin floors, grass and oak higher up, and pinyon, juniper and even relict Douglas fir in the highest canyons. Rainfall on the basin floors runs under 12 inches a year and El Paso averages under 10, but the mountains catch enough summer storms to hold pine forest. Because there is no cloud cover, no humidity and almost no light, the Davis Mountains hold some of the darkest skies in the continental United States, which is why the University of Texas put McDonald Observatory there.
Farming is possible only where there is irrigation: cotton, pecans and alfalfa in the El Paso valley below the city, alfalfa and melons along the Pecos around Pecos and Balmorhea, and onions in the Presidio valley, where winters are warm enough to crop in January. Everywhere else the land is ranched at very low stocking rates, or held as park. Balmorhea State Park's pool is fed by San Solomon Springs, which pour out of the ground at the foot of the Davis Mountains.
The drilling is concentrated in the northeast. The Delaware Basin — the western half of the Permian Basin — lies under Reeves, Culberson, Pecos and Loving counties, and horizontal drilling there is the reason Reeves County's population and truck traffic climbed after 2010. West of the Salt Basin there is almost nothing but ranch road.
Records
| Highest point in Texas | Guadalupe Peak, 8,751 ft, Culberson County |
| Largest county in Texas | Brewster, 6,193 sq mi |
| Least populous county in the U.S. | Loving, on the Pecos at the New Mexico line, with 64 people in 2020 |
| Largest national park in Texas | Big Bend, 801,163 acres in Brewster County |
| Largest state park in Texas | Big Bend Ranch, about 311,000 acres in Presidio and Brewster counties |
| Only Texas counties on Mountain Time | El Paso and Hudspeth |