Before drainage channels were built to divert water to the sea, the rain that fell on the foothills of the Santa Ana Mountains and slopes of the San Joaquin Hills settled in the lowland creating a vast waterlogged marshy ground.
This lowland, an early Orange County landmark that stretched from Upper Newport Bay almost to Red Hill, was known to Spaniards and Californians as the Cienega de las Ranas (The Swamp of the Frogs). It was covered with willows, tules and guatamote and had long been the dwelling place of millions of tree frogs.
During the winter none of this area could be crossed, even on horseback, but in the spring and summertime, when travelers did cross the swampland on that stretch of the Camino Real, they took their bearings from the frogs' collective high-pitched chorus. On dark nights, travelers were guided by the singing of these frogs and knew they were close to Red Hill, formerly known as the Hill of the Frogs.
The tract sometimes called Cerrito de las Ranas and sometimes Cienega de las Ranas was once part of the three large grants that went into the making of the Irvine Ranch that was known as San Joaquin.