Big Bend National Park -
http://www.bigbendguide.com/ There are many areas of the Park including twenty seven miles of the Rio Grande River. The river portion extends from just south of Presidio and journeys downstream to Lajitas. This area includes campgrounds, picnic areas, and trail heads. The interior consists of the original ranch headquarters and includes lodging and camping. This once privately owned land is now the property of the State of Texas. It has been developed into a State Park and is run and operated as such. It is possibly the most unique Park in the System. It is the largest, encompassing nearly 300,000 acres, and is considered a pristine wilderness. A guided desert tour is available for experiencing a multi-day trip into the backcountry of the Big Bend area. Features trails like Gualle Mesa, Madrid / Mexicano Falls, Sollitario, Topado Canyon, Panther Canyon, Palo Amarillo, Papalote Alto, and Smith Springs.
"Big Bend National Park Official NPS Website -
Dead Link Removed For what it's worth: there are some trails in Colorado that are listed as "4WD high clearance only" that I've seen 2WD grocery getters manage just fine. In other words, you can't always trust what a "vacation" guidebook (website) tells you." - Alan Hatcher
"Big Bend National Park is where Black Gap Rd. is, the location is out the Glen Springs Rd. down towards Mariscal mountain. The link you posted was for some guide in west Texas here is the park link if you don't have it
Dead Link Removed" - River Rat
"I found this on “backcountry dirt roads” in Big Bend, read about the river road
Dead Link Removed" - Jimmy Mancuso
"None of those roads are really difficult, but they do change season to season and get washed out in parts. I took my '79 jimmy on 35'' through must of them and never had to put her in 4wd. It would be more difficult if it rained.
By picking the right line (avoiding the large loose rocks ) the only problems is the width at times as some of them have a drop of in one side with part washed out. Black Gap road can be driven by a stock vehicle and probably a car if carefully picking the right lines.
I believe the 3 picture in the web page Jimmy sent is the hardest place in Black gap, and you can even see in the picture that they have smoothed it out by putting concrete with rocks to make it an even grade. Still fun.
But it is a great place and well worth traveling to, just don't expect extreme trails, they are just difficult enough to keep you on your toes as the dirt roads are full of holes, trenches and small/medium sized rocks.
There is supposed to be some difficult trails north of Terlingua but I don't have any information, and there are some ghost towns that were discussed in here not long ago.
The scenery and the solitude are incredible, and the hiking is excellent in and out of the Chisos Basin. I f you haven't been to this area of Texas you need to see it. I do highly recommend it." - Javier