The Old San Antonio Road is the most well-known and well-preserved route of El Camino Real de los Tejas, or "The royal road of the Tejas," - a major overland route across Texas used from the 1600s to 1800s. The Old San Antonio Road was surveyed in 1915, before any paved roads existed in Texas. Much of the route has been preserved by State Highway 21 and other state or U.S. highways. Other parts of it still exist as paved or unpaved local roads. In some places, it exists only as a barely-visible trail or brush clearing. Other parts of the road have completely disappeared from the ground, and exist only as a line on a survey sketch.

The following pages provide a county-level tour of the Old San Antonio Road. Each page begins with a map of the county with the route of the Old San Antonio Road from V.N. Zively's 1915 survey superimposed on it, so you can see which modern roads, if any, follow the route. Then, the article takes you on a tour of the road, from east to west, with photographs and descriptions of the road, the towns, and interesting and historic places along the way, all the way from the Sabine River to the Rio Grande.

In 1918, the Daughters of the American Revolution and the state of Texas placed 123 pink granite markers along the Old San Antonio Road to preserve it for future generations. Most of these markers still exist, although some have been moved, and some have been lost. Because these century-old markers are now a subject of historical interest in their own right, we have special county-by-county tour pages set up just for the markers. The marker tour pages use the same maps as the main tour pages, but they focus exclusively on the markers, with measurements and descriptions of the stones and detailed directions and geographic coordinates for finding them.