 Río Blanco was founded as a mining camp in 1691 when deposits of mercury, silver, gold and water for processing were found by the Spanish.However, Peñamiller and the rest of the Sierra Gorda of Querétaro were not subdued and settled until the expedition of José de Escandón in the mid 18th century, culminating in the defeat of the Chichimeca Jonaz and allies at the Battle of Media Luna (in neighboring Pinal de Amoles) in 1748.The municipal seat was founded in 1748, at first with a military aim of a fortress against the scattered Chichimecas who had escaped the Battle of Media Luna.