San Antonio de Béxar Presidio, the center of Spanish defense in western Texas, was founded by Martín de Alarcón on May 5, 1718, on the west side of the San Antonio River one-fourth league from the San Antonio de Valero Mission. In 1722 the Marqués de Aguayo relocated the presidio almost directly across the river from the mission. The presidio at that time was housed in one adobe building thatched with grass; the soldiers lived in brush huts. Because of its proximity to the Rio Grande and the better organized missions in its vicinity, Béxar did not suffer want and distress as did the other presidios. In 1726, when Pedro de Rivera made his report, there were forty-five soldiers at San Antonio de Béxar. Nine additional soldiers were on mission guard or escort duty, and four settlers and their families lived near the presidio, as did the families of the soldiers. The total Spanish population was estimated at 200. Rivera recommended that the complement of the presidio be cut from fifty-four to forty-four and reported that the captain was efficient and the soldiers well-disciplined.
Although recommendations were made periodically that permanent fortifications be erected, no wall or stockade was ever built. In May 1763 Luis Antonio Menchaca, who relieved Toribio de Urrutia as commander, reported that the garrison consisted of twenty-two men, of whom fifteen were assigned to mission guard duty, leaving five in addition to the captain and sergeant in the presidio. The presidio was charged with the protection of five missions and a civil settlement and in addition was supposed to furnish escorts for officials and missionaries, take messages from one post to another, and convoy supply trains. Menchaca also reported that, although the soldiers at San Antonio de Béxar were well-armed and well-disciplined, the number was inadequate for so important an outpost, especially since there was no breastwork for defense and the area was exposed to frequent attacks by Indians.
In 1772 the Marqués de Rubí recommended that San Antonio de Béxar be allowed to remain even though it was out of the semicircular defense line that he advocated. The withdrawal of the presidios of San Sabá, San Agustín de Ahumada, and Nuestra Señora del Pilar de los Adaes, as recommended by Rubí, left San Antonio de Béxar the northernmost Texas outpost of New Spain. Rubí's recommendation that San Fernando de Béxar, the civil settlement surrounding the presidio, be made the capital of Texas, was also followed. The Reglamento é instrucción para los presidios, issued in 1772, increased the garrison at San Antonio de Béxar to eighty men, the additional troops to be transferred from Nuestra Señora del Pilar de Los Adaes and San Agustín de Ahumada, and stipulated that twenty of the men were to be detached under a permanent lieutenant on Cibolo Creek to protect the ranches of the settlers and to keep open communications with La Bahía del Espíritu Santo. The regulations further provided that the captain of the presidio would also serve as governor of the province.
In December 1790 Pedro Huizar was commissioned to draw plans for the reconstruction of the presidio and improvement of its defenses, but the plans were not acted upon. The Second Flying Company of San Carlos de Parras was sent to reinforce the presidio in 1803. In 1805 Manuel Antonio Cordero, making use of the discretionary powers granted him as governor, began the construction of a stockade along the northern and northeastern limits of the city and planned to build permanent quarters for the troops, a stockade around the presidio, and a small fort. His plans were not completed, however, for in 1806 the soldiers were stationed on the east side of the river near the Alamo, which had ceased to function as a mission and had become the chief building for the military. To the end of Spanish and Mexican Texas, the Alamo remained the principal unit of walled defense, while the two plazas, Military Plaza and Plaza de la Islas (the plaza names changed in 1836), separated by San Fernando Church (changed in 1874 to San Fernando Cathedral) and the priests' house, served as the center of municipal defense. A lookout fort was located across the river 1 ¼ miles from town.
Aside from Indian defense, Béxar Presidio became involved in hostilities during the Mexican and Texan wars of independence. Led by a retired militia officer, Juan Bautista de las Casas, the garrison rebelled against its Royalist officers in January 1811 (see CASAS REVOLT). The unit's loyalty to the crown was soon restored, and the garrison was part of the army with which Manuel de Salcedo fought the Gutiérrez-Magee expedition in 1812–13. Ousted for the first time from the city as a result of Gen. Martín Perfecto de Cos's defeat by Texan forces in December 1835, the garrison was briefly reinstated after the fall of the Alamo in March 1836. The presidio formally ceased to exist with the garrison's acknowledgment of Texas independence and surrender on June 4, 1836.