In the late 1850s the rangers fought vicious battles with the Comanche, and in the Civil War, Terry's Texas Rangers gained renown. In the Reconstruction era the Texas Rangers were engaged to control outlaws, feuding groups, and Mexican marauders and were responsible for keeping law and order along the Rio Grande. In 1874 the Texas Rangers were organized for the first time on a permanent basis in two battalions; one was assigned to arbitrate range wars on the frontier, and the other was sent to control cattle rustling on the Texas-Mexico border. The heyday of the great cattle business, with its feuds and shootings, its outlaws and rustlers, was also the heyday of the Texas Rangers.

In the 20th cent. the police responsibilities of the rangers, around whom much lore had built up, decreased, and by 1935 their numbers had diminished considerably. By act (1935) of the Texas legislature, the rangers were merged with the state highway patrol under the jurisdiction of the state department of public safety. The rangers now form an elite investigative squad within the Texas highway patrol. The first women rangers were admitted to the force in 1993.