What happens to the elevation of Texas if you travel from Southeast west Texas?

As you travel from southeast Texas to west Texas, the elevation generally increases.

Southeast Texas is mostly dominated by the Gulf Coastal Plain, which lies just above sea level. The elevation of this area is typically less than 100 feet above sea level. As you travel westward, the landscape shifts towards the Edwards Plateau and Trans-Pecos regions. These areas have higher elevation, with the Edwards Plateau reaching an average of 1,000 to 2,000 feet above sea level and the Trans-Pecos region reaching elevations up to 8,000 feet in the Guadalupe Mountains, near El Paso.