San Francisco Xavier de Gigedo Presidio was a Spanish military outpost founded on March 30, 1751, on the south bank of the San Gabriel River (known then as the San Xavier River) to protect and aid the San Xavier missions. The presidio was located about five miles from the present site of Rockdale, Milam County. The garrison remained at the presidio until 1755, when disease and drought forced the soldiers to flee with the missionaries and their neophytes to the San Marcos River. The following year the garrison was reassigned the duty of protecting the San Sabá missions in Lipan Apache territory.
Before the formal establishment of the presidio, the three San Xavier missions, which included San Francisco Xavier de Horcasitas, Nuestra Señora de la Candelaria, and San Ildefonso, received protection from soldiers on temporary assignment from Los Adaes, San Antonio, or La Bahía. The temporary force never adequately protected the missions from Apache raids, however, and the missionaries complained that the soldiers set a bad example for the Indians. The soldiers also refused to aid the friars in recovering neophytes who wandered away from the missions. As soon as the missions were formally established, the College of Santa Cruz de Querétaro, sponsor of the missions, petitioned royal authorities for a regular presidio to ward off Apache raids and French incursions. The governor of Texas, Pedro de Barrio Junco y Espriella, opposed the mission project from the beginning and advised the viceroy in Mexico City against sending a regular garrison to San Xavier. The governor also refused to cooperate with efforts to keep the garrison at full force. Despite the governor's objections, Viceroy Francisco de Güemes y Horcasitas, Conde de Revilla Gigedo, sent Capt. José Joaquín de Ecay Múzquiz to select a location for a presidio on the San Gabriel River in 1750. In December 1751 Capt. Felipe de Rábago y Terán, the new presidio commander, arrived at San Xavier with a force of fifty men. From the moment of his arrival, the captain urged that the missions be moved to a better location. His relations with the missionaries deteriorated rapidly, and they petitioned for replacement of the garrison with a civilian settlement. Before the royal government could act on the suggestion, Rábago was implicated in the murder of a missionary, Fray Juan José de Ganzabal, and a Spanish soldier at Mission Candelaria and was removed from office. The resulting scandal reopened the issue of moving the missions to a better location. In 1755, after suffering drought, disease, neglect, and Indian desertions, the commander of the presidio, without authorization, ordered his garrison and the missions to withdraw to the San Marcos River. Most of the Indian neophytes joined the San Antonio missions. The presidio company was assigned to the new San Luis de las Amarillas Presidio on the San Saba River by early 1757.