1764MapOjoDeAgua(fullsize-lowres)

An historic map from 1764 that shows today’s Blue Hole at the far left side. The spring is labelled "Ojo de Agua" and is shown as the source of the San Antonio River. All five Spanish Missions are shown downstream along the river. San Pedro Springs are shown, and also labelled "Ojo de Agua," which is a common name given to springs. Photo courtesy Headwaters at Incarnate Word, Inc.

An historic map from 1764 that shows today’s Blue Hole at the far left side. The spring is labelled “Ojo de Agua” and is shown as the source of the San Antonio River. All five Spanish Missions are shown downstream along the river. San Pedro Springs are shown, and also labelled “Ojo de Agua,” which is a common name given to springs. Photo courtesy Headwaters at Incarnate Word, Inc.

An historic map from 1764 that shows today’s Blue Hole at the far left side. The spring is labelled “Ojo de Agua” and is shown as the source of the San Antonio River. All five Spanish Missions are shown downstream along the river. San Pedro Springs are shown, and also labelled “Ojo de Agua,” which is a common name given to springs. Photo courtesy Headwaters at Incarnate Word, Inc.