When the Spanish frontier expanded northward from central Mexico, the presidio, the mission, and the civil settlement became related frontier institutions for supporting Spanish colonization. Spanish missions generally were accompanied by presidios. Martín Enríquez, fourth viceroy of New Spain (1568–80), is generally credited with originating the presidios of the Southwest. He ordered the construction along the main road from Mexico City north to Zacatecas of casas fuertes ("fortified houses"). Eventually the name was changed to presidio (from Latin praesidium, "garrisoned place"). The pattern of the early presidios was learned from the Moors and dated from the days of the reconquest in Spain. By the early eighteenth century, when Spaniards settled Texas, it had changed but little.
The presidios in Texas were Nuestra Señora de los Dolores de los Tejas (1716), San Antonio de Béxar (1718), Nuestra Señora de Loreto and Nuestra Señora del Pilar de los Adaes (both 1721), San Francisco Xavier de Gigedo (1751), San Agustín de Ahumada (1756), San Luis de las Amarillas (1757), and (1789). San Elizario Across the Rio Grande, other presidios important to Texas included Presidio del Norte, San Juan Bautista, and San Gregorio de Cerralvo. Presidio soldiers engaged in military operations from the Pecos River to the Red River, among them the campaigns of Vicente Rodríguez and Diego Ortiz Parrilla. Each presidio had a specific role. Dolores protected the 1716 missions in East Texas and served as a listening post on the French. Loreto (also known as La Bahía Presidio) patrolled the coast against invaders and rescued shipwreck victims. Los Adaes countered the Louisiana French established at Natchitoches. San Agustín curbed French trading activities along the coast. San Luis de las Amarillas (also known as San Sabá Presidio) served as a buffer for San Antonio against raids by the northern tribes (Norteños), including Comanches.
Presidios were constructed of local building materials (sometimes adobe, sometimes log). Where stone was available it was preferred for the permanent structure. The forts were typically square or rectangular with some walls ten feet high. On two diagonal corners, round bastions (torreones) were placed. These rose above the walls of the presidio and were pierced with firing ports, through which soldiers could fire down the length of all four walls at attackers. There were occasional variations, as at Los Adaes in East Texas, which had wooden palisades and diamond-shaped bastions. Buildings were contained by walls eighteen feet apart, the roofs of which were high enough to serve as parapets from which men also could fire over the walls. A presidio included storage facilities, a chapel, and quarters for officers and men. The only openings were a main gate, which locked from the inside, and sometimes a rear gate. The two urban presidios on the northern frontier, at San Antonio and Santa Fe, had no walls, no towers, and no barracks, although the presidio at San Antonio was enclosed by a stockade, as Governor Domingo Cabello y Robles reported in 1781. In both cases the residence of the governor-captain was situated on the town plaza, as also were a guardhouse and the chapel, while the soldiers lived in their huts in town. The systems of fortification being developed in Europe during the eighteenth century by such men as French military engineer Sébastien le Prestre (the Marquis de Vauban), who died in 1707, and Menno van Coehoorn had only slight influence on frontier Spanish presidios. The Indians of the region had no cannons with which to blast fortress walls, and most officers in frontier service were slaves to tradition. Thus they continued to rely on traditional, inexpensive designs and materials that produced forts little different from the fortresses erected in Spain during medieval days.
Presidio soldiers assigned to protect the missions also conducted supply trains, escorted missionaries, colonists, and merchants, carried the mail, and explored the country. At the missions, soldiers' aggressiveness and conduct toward Indian women occasionally caused problems. The soldiers usually brought families or else married local Christian natives. Their families constituted a permanent Spanish population in the new land. Conferences with Indians were conducted at presidios, which thus functioned as frontier Indian agencies. The presidios were oases of safety for travelers who camped in their shadows. Around them the soldiers and their families built homes. Merchants came to sell goods, farmers came to plant their crops, and small civil settlements grew.
The soldiers in these presidios lived lives of considerable hardship and danger. When the Marqués de Rubí inspected the northern frontier, including Texas, in 1766–68, he found an almost total lack of discipline. Soldiers had not been instructed in using their firearms, most of them were deeply in debt because their salaries were in arrears, and their equipment and arms had badly deteriorated or were lacking altogether. Officers were profiteering by selling inferior goods to the soldiers at inflated prices, and morale was shot through with insubordination. Rubí sought not only to correct abuses, but to withdraw from the desired frontier to a real one and take up more defensible positions. He recommended that the presidios of the northern frontier be reorganized into a chain of fifteen forts stretching from the Gulf of California to the Gulf of Mexico, each approximately forty leagues from the next to allow quick communication and the rapid dispatch of help. The soldiers in the garrisons were to be properly equipped, regularly paid, and carefully instructed in their duties. Despite the efforts of Rubí and other high officers on the northern frontier, soldiers stationed in the fifteen presidios and capital cities of San Antonio and Santa Fe were never able to conquer the Comanches, Apaches, Navajos, and other nomadic warring tribes for two reasons. First, the strategy of building forts across the northern frontier was based on concepts of European warfare. In the Old World, armies would advance on a fortified city and halt to invest it. If they failed, they retreated. The Indians in the New World saw no reason to attack a presidio; they preferred to ride around it to attack civilian settlements, ranches, and farms. Second, each Spanish soldier was so burdened with weapons and equipment that he needed some six mounts to undertake a campaign. Presidial compounds were not large enough to hold the horses, which therefore had to be picketed some distance away from presidios-and thus were conveniently gathered for Indians to steal. The presidial soldiers could not pursue the raiders because they were left afoot. For all their shortcomings, however, Spanish presidios served a useful purpose on the northern frontier. Their design was so practical that the Indians of the region never were able to overcome one by frontal assault, although they did penetrate a few by stealth. Many American traders and military leaders of a later date recognized the basic worth of presidios and chose to build their forts in the Southwest on the same pattern. The restored Presidio La Bahía at Goliad stands today as a state monument to the Spanish presidio.