Old San Antonio Road

The Old San Antonio Road, the Spanish colonial route also called the Camino Real and the King's Highway, crosses Interstate 45 on the line between Madison and Leon counties, and for miles west of the crossing the old road is the county line itself. It took shape in the 1690s as the path of Spanish expeditions to the East Texas missions, led by Alonso De León in 1690, Domingo Terán de los Ríos in 1691 and Gregorio de Salinas Varona in 1693. It became the main overland route into Spanish Texas, carrying supplies and soldiers to the missions, cattle drives bound for the fair at Saltillo, and later Anglo-American settlers; Moses Austin travelled it to San Antonio in 1820. It was never one road: a 1991 state study identified at least five main routes used at different times.

The section between Bastrop and Crockett, which passes between Madison and Leon counties, came into use only after 1790. In 1915 the legislature appropriated $5,000 to survey and mark a route, and surveyor V. N. Zivley traced one version from the Rio Grande to the Sabine, 540 miles. The Daughters of the American Revolution set granite markers along it in 1918; by 2015 only 34 of the 110 that had been found still stood within 100 feet of their original places.

In 1929 the legislature named Zivley's line a historic trail. The stretch from Midway west past Normangee became a state highway that year and was renamed State Highway OSR in 1942, the only Texas state highway designated entirely by letters. The colonial road ran about 2,500 miles from Mexico City to Los Adaes in Louisiana, and the National Park Service commemorates its Texas and Louisiana routes, some 2,580 miles of them, as El Camino Real de los Tejas National Historic Trail.