San Marcos br/Hays County, Texas br/29 53.013' N 97 56.217' W br/br/Text: Situated here in 1846, at call of the United States for volunteers to establish the Rio Grande as the United States-Mexican Border, after the annexation of Texas. For centuries a campsite for Indians and other travelers of El Camino Real. San Marcos Springs were of great importance in event of Mexican or Indian Invasions. Also, soldiers based here could go quickly to the relief of San Antonio or the State Capital. Commanded by Capt. Henry L. McCullough (1816-95), noted frontier fighter, ex-sheriff at Gonzales, the post in a year's time enrolled 189 mounted volunteers. The company saw action as scouts on both sides of the Rio Grande, and overawed menacing Indian tribes. The mounted volunteers furnished their own horse, guns, and equipment. Some of these men had fought in the 1835-36 War for Independence, many had served the Republic of Texas as Rangers. Residents of this area, some protected their families by bringing them along to the four houses of settlers already here. They added a few crude dwellings and opened a school. The one recorded building of the military post was commissary-corncrib. The camp bordered the river. In July 1847 the company was restationed 100 miles north, to patrol the wilder Llano and Lampasas Rivers.