Pablo Perez, a principal founder of San Diego, Texas, was born in Mier, Tamaulipas, Mexico, on May 14, 1812. In 1848–49 Col. Henry L. Kinney, in partnership with Gen. William L. Cazneau, was marking a wagon-train route from Corpus Christi to Laredo, to go through San Diego Ranch in what is now Duval County. At the same time Perez bought land across the creek from the ranch headquarters, built several stone houses, and brought in settlers. The settlement was called Perezville. It and the San Diego Ranch headquarters united, qualified for a post office in 1852 under the name San Diego, and appeared on state maps as a town. In 1850 Perez married Vicente Barrera, daughter of Manuel Barrera and heir to the La Tinaja de Lara land grant and the Amargosa Ranch. During the later 1850s Perez established two more ranches on the grant-Los Reales and El Muertecito-which he later sold.
In 1852 the area between the Nueces and the Rio Grande experienced a series of outlaw and Indian raids. After an Indian raid made the Amargosa Ranch owners flee to Mier for safety, strangers moved onto the ranch. Felix von Blücher, official surveyor of the San Patricio District, in 1854 surveyed the Tinaja de Lara grant for Perez as a step in reclaiming it. In 1860 Perez persuaded the heirs and assignees to bring suit to regain title, which was awarded to them. In 1867 Perez bought a large tract of the Charco de los Preseños grant and sold a portion of it to N. G. Collins, founder of the short-lived town of Collins, in order to entice the Texas-Mexican Railway to build through Collins en route to San Diego. Pablo and Vicente Perez had four sons and two or three daughters. Vicente died on February 21, 1876. For proof of ownership and tax purposes, Pablo filed an inventory of the property his wife left him. This, added to his own extensive holdings, proved him to be a very wealthy man. Perez died on May 29, 1892, and was buried in the San Diego Cemetery.