This is part of Amistad National Recreation Area and Spur 406 has a small, 6 site campground with tables and a vault toilet. There’s also dispersed camping south of the campground. Turn left on the dirt road after passing the toilet. We stopped at the first clearing but the road continues down to the lake where it opens up to a large clearing. The road is narrow and has a muddy spot with deep ruts. Almost any vehicle will scrape bottom and possibly get stuck. Since it doesn’t appear to get any maintenance by the park, if you want to use the road you’ll have to fill the ruts yourself. The reward is a great camping spot right on the water when the lake is high.
Spur 406 continues past the dispersed camping turn off and dead ends at Amistad Lake. The water level of the lake fluctuates depending on the amount of rainfall but it’s been slowly rising over the last few years and is now just 17’ below the full level. Depending on the water level, there may be no place to turn around. Walk to this spot and the dispersed camping areas if you’re unsure of the conditions.