I haven't been there, but has you tried the "Allstays" Camp and RV app from Apple? It shows that there is a campground right outside Dumas, and several State Park campgrounds in the area. It's a free app and holds a wealth of information, with a basic overview of the campgrounds along with reviews, phone numbers and links to the campground's website if they have one. It will also show truck stops, Walmarts and the such.
Retired Army CW4 - "Waterborne"
2005 Chevy 2500 crew cab with Duramax/Allison
2014 Lacrosse 327RES
Days camped 2014 - 0, 2015 - 24