Pilares was a village located in northwest Presidio County, Texas, United States, on the southern boundary of the Sierra Vieja near the Rio Grande. The river village was 1.25 miles (2.01 km) south of the confluence of Quinn Creek and the Rio Grande while bearing 1.5 miles (2.4 km) north of Porvenir, Texas. The uninhabited site is in the Trans-Pecos region of West Texas with a southern panorama of the Chihuahuan Desert and northern Mexico.

Presidio de Pilares, also known as El Principe, was established along the southern boundaries of the Rio Grande basin in the northern Chihuahua territory of New Spain in 1774. The Spanish Presidio provided a defensive wall against the native plains inhabitants during the Mexican Indian Wars in Spanish Texas.

In the mid-18th century, Charles III of Spain appointed Marquis of Rubí and José de Gálvez to fulfill expeditions and observations of the America frontier presidios in the northern regions of New Spain.

On September 10, 1772, the Spanish Empire issued new regulations for presidios constructed in New Spain near the Rio Grande in the Northern Mexico territories. In 1776, the Viceroyalty of New Spain established Spanish provinces in the Spanish America frontier through the governance of the Provincias Internas serving as a supplemental article to the Bourbon Reforms. The Spanish Presidio coerced the territorial development of New Spain in the Chihuahua territory of the Spanish America colonies while fortifying the Spanish missions in Texas.

• Adams–Onís Treaty
• Comanche Trail
• French colonization of Texas
• List of ghost towns in Texas
• Nueva Vizcaya, New Spain
• United States Camel Corps

• History of the Conquest of Mexico public domain audiobook at LibriVox

• Solís, Antonio de (1724). The History of the Conquest of Mexico by the Spaniards. London: T. Woodward and J. Hooke. OCLC 1046514488 – via Internet Archive.
• Solís, Antonio de (1738). The History of the Conquest of Mexico by the Spaniards. Vol. I. London: John Osborn. OCLC 733087530 – via Internet Archive.
• Solís, Antonio de (1738). The History of the Conquest of Mexico by the Spaniards. Vol. II. London: John Osborn. OCLC 733087530 – via Internet Archive.
• Bonnycastle, Richard Henry (1818). Spanish America; A Descriptive, Historical, and Geographical Account of the Dominions of Spain in the Western Hemisphere, Continental & Insular [Account of Spanish America]. Vol. I. London: Longman, Hurst, Rees, Orme, and Brown. OCLC 298513594 – via Internet Archive.
• Bonnycastle, Richard Henry (1818). Spanish America; A Descriptive, Historical, and Geographical Account of the Dominions of Spain in the Western Hemisphere, Continental & Insular [Account of Spanish America]. Vol. II. London: Longman, Hurst, Rees, Orme, and Brown. OCLC 981299968 – via Internet Archive.
• Bonnycastle, Richard Henry (1819). Spanish America; A Descriptive, Historical, and Geographical Account of the Dominions of Spain in the Western Hemisphere, Continental & Insular [Account of Spanish America]. Philadelphia, Pennsylvania: Abraham Small Publisher. OCLC 1157455578 – via Internet Archive.
• Bolton, Herbert Eugene (1915). Texas in the Middle Eighteenth Century: Studies in Spanish Colonial History and Administration. Berkeley, California: University of California Press. OCLC 558670456 – via Internet Archive.

• United States Geological Survey. Quinn Creek, TX quadrangle, Pilares, Texas (Topographic map). Reston, VA: United States Geological Survey – via TopoQuest.

• "Spanish Missions, Presidios, and Roads in the 17th and 18th Centuries". Perry-Castañeda Library Map Collection. University of Texas at Austin. 1976.
• "The Gateway Missions" [Attempts at Native Conversions along the Rio Grandé]. Texas Beyond History. University of Texas at Austin.
• "The Threads of Memory: Spain and the United States". Threads of Memory Exhibition ~ New Mexico History Museum. New Mexico Department of Cultural Affairs.