El Camino Real de los Tejas National Historic Trail

The El Camino Real de los Tejas National Historic Trail, also known as the Old San Antonio Road, is a national historic trail covering the U.S. section of El Camino Real de Los Tejas, a thoroughfare from the 18th-century Spanish colonial era in Spanish Texas, instrumental in the settlement, development, and history of Texas. The National Park Service designated El Camino Real de los Tejas National Historic Trail as a unit in the National Trails System in 2004.

The modern highways Texas 21 (along with Texas OSR) and Louisiana 6 roughly follow the original route of the trail.