Governor's Landing Campground in the Amistad National Recreation Area. My site overlooked these bridges (one for US 90, the other for the railroad) across Amistad Reservoir, which is a dammed section of the Rio Grande. (Perhaps damned, as well.)
scenic overlook/picnic area. Texas lets people stay 24 hours in any of their rest areas or picnic areas, though there aren't many you'd choose to, since most are barely off the highway. This was a good one, though. Fine view, tolerable traffic noise. Zero cell signal, though.
The Pecos meets the Rio Grande not far from this spot. I've also camped near the headwaters of the Pecos, in the Sangre de Christo mountains of New Mexico. So that's one end and the other, for whatever that wins me. Experiences, I guess, which are good things.