This thesis explores the history behind the creation of Texan boundaries. The boundaries of Texas were the cause of disputes between the French, the Spanish, Mexico, and later the United States of America. The intensity of these disputes threatened to disrupt the Union itself, and caused a war between the United States and Mexico.

The Texas Ranger tradition of over twenty-five years of frontier defense influenced the methods by which Texans provided for frontier defense, 1861-1865. The elements that guarded the Texas frontier during the war combined organizational policies that characterized previous Texas military experience and held the frontier together in marked contrast to its rapid collapse at the Confederacy's end. The first attempt to guard the Indian frontier during the Civil War was by the Texas Mounted Rifles, a regiment patterned after the Rangers, who replaced the United States troops forced out of the state by the Confederates. By the spring of 1862 the Frontier Regiment, a unit funded at state expense, replaced the Texas Mounted Rifles and assumed responsibility for frontier defense during 1862 and 1863. By mid-1863 the question of frontier defense for Texas was not so clearly defined as in the war's early days. Then, the Indian threat was the only responsibility, but the magnitude of Civil War widened the scope of frontier protection. From late 1863 until the war's end, frontier defense went hand in hand with protecting frontier Texans from a foe as deadly as Indians—themselves. The massed bands of deserters, Union sympathizers, and criminals that accumulated on the frontier came to dominate the activities of the ensuing organizations of frontier defense. Any treatment of frontier protection in Texas during the Civil War depends largely on the wealth of source material found in the Texas State Library. Of particular value is the extensive Adjutant General's Records, including the muster rolls for numerous companies organized for frontier defense. The Barker Texas History Center contains a number of valuable collections, particularly the Barry Papers and the Burleson Papers. The author found two collections to be most revealing on aspects of frontier defense, 1863-1865: the William Quayle Papers, University of Alabama, and the Bourland Papers, Library of Congress. As always, the Official Records is indispensible for any military analysis of the American Civil War.