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 (the generally accepted "birth year" of the road), 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.