Texas triangle - this is the area bordered by I-35 to the west, I-45 to the east and I-10 to the south. It includes the metros of DFW, Houston, San Antonio and Austin as well as a few other smaller metros. The 60,000 square mile area contains more than 75% of the state's population.
http://en.wikipedia.org/wiki/Texas_Triangle
Texas triangle - 18,047,849
Dallas-Fort Worth-Arlington, TX 6,725,448
Houston-Sugar Land-Baytown, TX 6,281,135
San Antonio-New Braunfels, TX 2,267,995
Austin-Round Rock-San Marcos, TX 1,869,645
Killeen-Temple-Fort Hood, TX 423,207
Waco, TX 242,929
College Station-Bryan, TX 237,490
I-35 corridor from DFW to Laredo - 11,794,428
Dallas-Fort Worth-Arlington, TX 6,725,448
San Antonio-New Braunfels, TX 2,267,995
Austin-Round Rock-San Marcos, TX 1,869,645
Killeen-Temple-Fort Hood, TX 423,207
Laredo, TX 265,204
Waco, TX 242,929
Along the coast from Houston to Brownsville - 7,533,514
Houston-Sugar Land-Baytown, TX 6,281,135
Corpus Christi, TX 435,112
Brownsville-Harlingen, TX 424,987
Beaumont-Port Arthur, TX 392,280
Along the border from El Paso to McAllen - 2,366,272
El Paso, TX 845,296
McAllen-Edinburg-Mission, TX 830,785
Brownsville-Harlingen, TX 424,987
Laredo, TX 265,204