I am completly in sync with you on the state park thing with cars and kids and rangers etc...but many of the state parks have excellent hike-only backwoods trails. Also, the national forests....Sam Houston, Davy Crocket etc. are open country where you can pack in and out. Here is an excellent resource for you to look at some of these trails.
http://www.amazon.com/Hiking-Backpac.../dp/0884153258
Happy Hiking!
Greg