 El Camino Real was established to link the chain of missions constructed in California by the Spanish invaders.The Cienega de las Ranas was a major obstacle along the Camino Real and was completely impassable during most winters.In other seasons, those who were traveling from the south by night relied on the singing of the frogs to guide them to Red Hill (called "Cerrito de las Ranas" or "Frog Hill" by the Spanish), which marked the northern edge of the swamps.