Terwilliger valley and the town of Terwilliger are way out among the Native American Reservations in southern California - north east of San Diego and south west of Palm Springs. The valley can be found just south of the "city" of Anza.

Should you be heading south from Anza on Terwilliger Road,
east of the valley, you might see this sign.

If you followed it, you would be on Bailey Road heading west
toward the town of Terwilliger.

There was a 6.0 earthquake near the valley in 1937

Below is a sketch showing the locations of various prehistoric American indian sites
in the area around Anza (just to the right of the legend)