The Old San Antonio Road, popularly known as El Camino Real, was one of Texas's oldest and most significant trans-Texas routes, but rather than a single fixed road it was a changing network of Indian trails, stream crossings, and exploration routes that served commerce, migration, and communication during the Spanish colonial period. Its paths shifted over time in response to weather, Indian relations, terrain, transportation, settlement, and security threats, including pressure from Apache and Comanche peoples. The first known recorded trans-Texas journey along this network came in 1691, when the Téran-Mazanet expedition crossed the Rio Grande and followed the Camino de los Tejas into East Texas, while other segments appeared later, including the Bastrop-Crockett portion after 1790 and the Nacogdoches-Alto segment about 1830. These caminos reales were major factors in the conquest and colonization of pre-Republic Texas, as Spanish authorities, alarmed by French ambitions such as La Salle's 1685 colonizing attempt, sent military expeditions northward and founded communities as way stations between frontier outposts, with San Antonio de Bexar becoming the first and the regional hub. Before Mexican independence in 1821, Spanish officials encouraged settlement between Bexar and Nacogdoches, and the routes adjusted to serve those communities. Intended in part for defense, the road network later became a channel for migration and resistance to Spanish rule, influenced the strategy of the Texas Revolution, and after the Republic of Texas was established it helped carry immigrants from the U.S. into the region. After the Mexican-American War, the Camino de Arriba regained prominence during the Gold Rush as a route from East Texas to San Antonio, and during the War Between the States it was used to move cotton, troops, and supplies. After the Civil War and economic decline, large segments were abandoned for shorter routes to new markets, and the remaining portions served mostly local needs. The road's lasting significance lies in its role as part of the oldest transportation, communication, and military network in Texas, functioning as a post road long before the Republic developed post roads, as a cattle trail long before the Chisholm Trail, as a military road linking forts on New Spain's northern frontier, and ultimately as a principal avenue of Anglo-American immigration into Texas.