This dissertation describes the various military outposts on the Texas frontier between 1866 and 1886. It is arranged geographically, with each chapter covering a major fort or geographical area and the smaller posts associated with it. Official military records and government reports serve as the primary sources of data. In 1866 when the United States Army returned to the defense of Texas after four years of civil war, the state's frontier lay open to depredations from several Indian tribes and from lawless elements in Mexico. The army responded to those attacks by establishing several lines of major forts to protect the various danger areas of the frontier. To extend its control and protection to remote, vulnerable, or strategically important points within its jurisdiction, each major fort established outposts. Two main categories of outposts existed in Texas, subposts and picket stations. Subposts served as permanent scouting camps or guarded strategic points or lines of communication. Picket stations protected outlying locations, such as stage stations, that were particularly vulnerable to attack. Because Indians raiding in Texas usually operated in fairly small groups, garrisons at outposts were similarly small. Company-sized detachments generally garrisoned subposts, and picket stations seldom held more than a dozen troops, often fewer. The army used outposts haphazardly during the first few years after the Civil War. Commanders developed standard tactics for outpost garrisons, but they failed to form a comprehensive strategy incorporating a series of outposts in the plan to pacify a particular region until the late 1870s. At that time, Colonel Benjamin Grierson and others began forming a systematic network of outposts in far West Texas. Concentrating his outposts at the region's few water sources, Grierson was able to use those posts as an effective part of a strategy that eventually brought an end to danger from Apaches in that part of the state.