Horsethief Canyon, is a canyon, the upper part of Summit Valley in San Bernardino County, California. Its mouth is at an elevation of 3,123 feet / 952 meters. Its head lies at 34°19′33″N 117°25′38″W at an elevation of 3,800 feet just east of the summit of Cajon Pass.
References
Horsethief Canyon Wikipedia(Text) CC BY-SA