In 1765 Malaguita Indians, natives of the Padre Island vicinity, brought to San Juan Bautista Mission on the Rio Grande reports that White invaders were settling on the "Islas Blancas" near the mouth of the Nueces River. The squatters were presumed to be English. The viceroy of New Spain, the Marqués de Cruillas, responded to this and other rumors of English activity along the Gulf Coast by ordering a two-pronged investigation. On November 2, 1765, he asked José de Escandón, colonizer and governor of Nuevo Santander, to gather all available information on the islands. The following April 19, before Escandón had reported, Cruillas called for exploration of the region by Diego Ortiz Parrilla, who had recently been relieved as interim governor of Coahuila and was serving as commandant of the Coahuila presidio of Santa Rosa del Sacramento. Ortiz Parrilla, the first commandant of San Luis de las Amarillas Presidio on the San Saba River in Texas, had officiated in the 1763 transfer of Pensacola to the British in the settlement of the Seven Years' War. Out of his coastal reconnaissance came the first map of Padre Island and the adjacent coast. His report, added to Escandón's, provided much detailed information on the barrier islands of Texas that had eluded previous Spanish explorers and mapmakers.
Escandón had responded to the viceroy's order by asking Capt. Blas María de la Garza Falcón of Camargo to report on the coast between the Rio Grande and Garza Falcón's ranch outpost, Estancia de Santa Petronila, "five leagues" south of the bay presently called Corpus Christi. In this vicinity, where Garza Falcón had been granted pasture and farm land, it was reported, he had settled "a goodly number of people." Garza Falcón and his son José Antonio de la Garza Falcón carried out a preliminary reconnaissance of Padre Island and reported to Escandón in a consulta dated June 18, 1766.
While waiting for the report, Escandón received information from José Antonio de Garabito, a native of Campeche, fisherman by trade and settler of Villa de Soto la Marina in Nuevo Santander. Garabito had lived a number of years at La Bahía Presidio (present Goliad). Though revealing an intimate knowledge of the lower Texas coast, he had found not a single foreigner. From Garabito, Escandón drew a description of the "large pastureland surrounded by lagoons," extending along the coast between the Rio Grande and the Nueces River. Only with storm surge, he said, was this area separated from the mainland; therefore it could not properly be called an island. From the mouth of the Nueces to the Bahía del Espíritu Santo (Matagorda Bay), he reported, lay a series of sandbanks that were completely inundated in times of high water.
Escandón, ordered to support Ortiz Parrilla's expedition, provided twenty-five soldiers led by the alferez José Antonio de la Garza Falcón. Ortiz Parrilla proceeded from Santa Rosa Presidio to San Juan Bautista, where he was joined by the mission Indians who had reported the invaders. After meeting the Nuevo Santander soldiers at the Estancia de Santa Petronila, he set up camp on September 7, 1766, on the beach referred to as Playa de la Bahía de Corpus Christi, or Playa de Corpus Christi. Thus it appears that this name was first applied to the Laguna Madre, which separates Padre Island from the mainland, not to what is now called Corpus Christi Bay. In the camp called Real de Santa Petronila, the company waited out six days of drenching rain and high wind triggered by the hurricane that had ravaged San Agustín de Ahumada Presidio and Nuestra Señora de la Luz Mission near the mouth of the Trinity River.
Garza Falcón began the Padre Island reconnaissance with the Nuevo Santander soldiers on September 13. He was assisted by another alferez, Eugenio Fernández; a coastal pilot, Mateo Martínez; and nine Malaguita Indians from the missions San Juan Bautista and San Bernardo. The mounted company crossed the shallow lagoon "two leagues" wide and trekked over a stoneless strip of barren sand from Old Corpus Christi Pass to the Brazos Santiago. The only trees were small clumps of stunted laurels and willows, the only herbage a red grass so unpalatable that the horses would scarcely eat it. The beach was littered with masts, spars, and bits of rigging from ships of all sizes. On Brazos Island lay the broken hulk of a twenty-gun English ship. There was no other sign of Europeans and no verification of the Indians' claim that foreign ships frequented the coast. The only Indian signs were abandoned rancherías at the lower end of the island, where Ortiz Parrilla's map indicates habitations of the Manos de Perro, Patrines, Piguisas, Pasnaaus, and Malaguita Indians. The company returned to report to Ortiz Parrilla on September 24. Martínez, who had piloted Escandón's schooner along the Mexican coast and reconnoitered the mouth of the Rio Grande from the Gulf, expressed surprise concerning the nature of the island. He had perceived no such islands along the entire Mexican coast between the Isla de Lobos and the Rio Grande. Yet the explorers acknowledged that the Isla de San Carlos de los Malaguitas, as they now called it, was continuous except for three storm passes, which in times of high water made it appear as four.
Unable to reach the mouth of the Nueces River because of the flooding, Ortiz Parrilla dismissed the Nuevo Santander soldiers to continue his mission with only his troop from Coahuila. Traveling "forty-two leagues" up the Nueces, he crossed at the Laredo-La Bahía road and proceeded to La Bahía Presidio. He reached the fort early in October and interviewed two soldiers just arrived from the devastated San Agustín Presidio and others who informed him that all the coastal streams and marshes were flooded. He concluded that further exploration would be impossible. He therefore proceeded to take additional depositions to round out his report on the coast from the Nueces to Galveston Bay.
With his report, dated May 4, 1767, Ortiz Parrilla submitted the map drawn under his direction depicting the Texas coast as he understood it from his own exploration and from the testimony taken at La Bahía. Although the map represents Padre Island fairly accurately, considering the circumstances of the reconnaissance, Baffin Bay is notably absent. What appears to be Corpus Christi Bay is shown apart from the Nueces River. At the lower end, Brazos Island appears in its proper place. The Arroyo Colorado, which enters the Gulf in southeastern Willacy County, is called Arroyo de San Miguel. The upper end of the island, separated from the lower part by a storm pass, evidently represents Mustang Island. On its northern tip are shown habitations of the Carancaguases (Karankawas), Copanes (Cópanos), and Piguacasas (Piguiques). Above Corpus Christi Bay, Copano Bay appears as Bahía de Santo Domingo, fronted by a small island of the same name. Beyond the coastal bend, which is too sharp and too far north, the map information suffers from want of Ortiz Parrilla's first-hand observation. Matagorda Island is shown as a peninsula cutting off San Antonio Bay on the west; Matagorda Peninsula, as Isla de Culebras, from the name given its western point (Punta de Culebras) by Juan Enríquez Barroto in 1687. Although Matagorda Bay is shown as Bahía del Espíritu Santo, the name San Bernardo, actually the more popular designation for Matagorda Bay, is applied to Galveston Bay, and Trinity Bay is called San Antonio. Galveston Island does not appear. River mouths and inland stream courses are similarly confused. Ortiz Parrilla, while negating rumors of an English settlement on the Texas coast, advanced official understanding of this region's geography considerably. In his own estimation, his report and map superseded "all those that have come to the courts of Spain and France." Yet it remained for such later explorers as José Antonio de Evia to overcome the three great stumbling blocks to an accurate assessment of the upper Texas coast: shallow bays, hurricanes, and Karankawas.