When I was in college, I drove out to my parents' ranch to read the electrical meter. (One thing about the country, you have to read your own meters.) I took one of my friends with me, and as we turned onto US-90, there was a sign that said "El Paso 560." She was from El Paso, and burst into tears because she hadn't realized how far from home she really was.
My thought was - "What would it be like to drive across the entire State?" (I am not alone in this goal, apparently. It's the short version of Route 66 or a Transcontinental Route.)
So, this is East to West - Beaumont to El Paso, with a round-trip from home in Dallas. It actually breaks into driving days pretty easily -
Heading Out
Dallas to Beaumont (298 miles)
Across Texas
Beaumont to San Antonio (277 miles)
San Antonio to Fort Stockton (314 miles)
Fort Stockton to El Paso (234 miles)
Heading Home
El Paso to Midland (298 miles)
Midland to Dallas (348 miles)