The Old San Antonio Road was a historic roadway located in the U.S. states of Texas and Louisiana. Parts of it were based on traditional Native American trails. Its Texas terminus was about southeast of Eagle Pass at the Rio Grande in Maverick County, and its northern terminus was at Natchitoches, Louisiana. The road continued from Texas through Monclova to Mexico City. The Old San Antonio Road is considered a part of El Camino Real de los Tejas National Historic Trail. Route Louisiana Highway 6 mostly runs alongside the Old San Antonio Road for the entirety of its route through that state from Natchitoches to west of Many. State Highway 21 follows the old road to Midway, Texas, then State Highway OSR (for Old San Antonio Road) follows it around Bryan and College Station, and back to Highway 21 to the eastern outskirts of San Marcos. South of San Marcos, the road follows the Old Bastrop Road until it intersects with I-35. The road leaves the Interstate at New Braunfels and follows Solms road, then Nacogdoches Road, then Mission Road through San Antonio. South of San Antonio, the road follows Old Pleasanton Road, then varying local and county roads and merges with State Highway 97 to Cotulla. The road crosses private property and then follows Farm to Market Road 133 to Catarina. After Catarina, the road is on private property. History In 1690, Spanish explorer Alonso de León, following various Indian and buffalo trails, crossed the Rio Grande on his way to East Texas to establish missions, effectively blazing the Old San Antonio Road. In 1691, Domingo Terán de los Ríos took additional missionaries to East Texas following much the same course as traveled by De León. In 1693, Gregorio de Salinas Varona further defined the course of the road while bringing relief supplies from Monclova. The Old San Antonio Road was not a single road, but a network of trails with different routes at different times. The trail's path was dictated by things as diverse as weather and Native American threats. During the time that Texas was a Spanish, then Mexican, state, the road was used as a major thoroughfare between Mexico City and East Texas. With Texas independence, however, trade between Mexico and Texas waned, while Mexico's trade with the United States began to increase. The old route from San Antonio to Louisiana, now called the Camino Arriba,