María Gertrudis de la Garza Falcón, owner of a large South Texas land grant in the eighteenth century, was born in 1734 in Cerralvo, Nuevo León, Mexico, to Blas María de la Garza Falcón and his wife, Catarina Gómez de Castro. Gertrudis was the sister of José Antonio de la Garza Falcón. When José de Escandón, governor of Nuevo Santander, undertook to establish settlements along the Rio Grande, Gertrudis's father was given permission to settle colonists at the confluence of the Río San Juan and the Rio Grande. The community thus established in March 1749 on the south bank of the Rio Grande was named Camargo. For defensive purposes, in order to ensure that the settlers would not disperse but remain concentrated, Escandón provided that most of the land would be held communally for a number of years.
Gertrudis's father was made captain of Camargo, and in 1750 Gertrudis, her stepmother, and her brothers moved to the new settlement. In 1754 Gertrudis married her cousin José Salvador de la Garza, son of Capt. Adriano de la Garza and María de Elizondo and also a resident of Camargo. The couple had three children. In 1767, when private land titles were issued to Camargo settlers, Salvador was awarded 5,757 acres of land on the north bank of the Rio Grande in what is now Starr County. Three years later, needing additional pasture, the Garzas moved some or all of their livestock about a hundred miles downriver to a site on the north bank across from Reynosa. In 1772 Salvador de la Garza applied for a large tract of land in this vicinity, title to which was granted him in 1781. The grant, known as the Potrero del Espíritu Santo (Pasture of the Holy Ghost), or simply as the Espíritu Santo grant, comprised 59½ leagues (284,416 acres) now in Cameron County. The ranch that Salvador de la Garza established on the grant was known as Rancho Viejo, and its headquarters were situated west of the site of present-day Brownsville. A state historical marker commemorating the ranch was placed beside U.S. Highway 77 five miles north of Brownsville in 1936.
After her husband's death, Doña Gertrudis became the owner of all the Espíritu Santo grant, with its cattle, horses, mules, sheep, and goats. Through her hands it passed to numerous descendants. In 1849 some of the family filed suit to recover the land on which the town of Brownsville was located, claiming that holders of faulty titles had improperly conveyed the land to Charles Stillman and the Brownsville Town Company. Although the Garza heirs won their case in January 1852, they sold the Brownsville tract the following April for one-sixth of its appraised value to the lawyers who had represented Stillman, and Stillman subsequently acquired the property. This litigation and the struggle of other Hispanics to retain their land in the face of mounting pressure, formed part of the social background for the activities of Juan Nepomuceno Cortina, a great-grandson of Gertrudis.
Doña Gertrudis died in 1789. Her will, dated August 18, 1789, stated that she wished to be buried in the Guadalupe Chapel in Camargo, where her father was buried. As late as 1991 some of her descendants still lived in the lower Rio Grande valley.