Look at a map of Texas. From around just west of Ft. worth, draw a line down to not far west of San Antoino, curving a bit out to the west--but not a lot--and then curving back toward corpus Christi. Unitl after the Civil War, that's about all of Texas that could be said to be controlled by either Texicans or the U.S. Everything northwest/west/southwest of that line was either Mexican outlaw or Indian territory.
Ranger groups worked the southwest and along the border trying to deal with the bandidos. Northwest of what's now Fredericksburg. and west of Fort Worth, figure Comanches. West of the Pecos it was more Apaches and Comances--who fought each other, as well.
The Comanche migration trail runs north-south, mostly from the upper Panhandle (summer territory) down into Mexico for the winter. They came through my area, crossing the Rio Grande at several points in Big Bend National Park and at Lajitas. They raided as far south as Monterrey, and once even to near Mexico City. The northernmost known point is at Dinosaur Monument in NW Colorado. Helluva horseback trip. There are still traces of the old trail, between Marathon and the Park mostly visible from the air.
The final Apache conflict in Texas was rather small; only some 15 or 20 of them. They were killed/captured by soldiers from Fort Davis. 1886, IIRC.