Seven Peaks of the Yucaipa Ridge Professional Review and Guide
"The Oak Glen Divide or Yucaipa Ridge, running parallel to and south of the San Bernardino Divide, separates Mill Creek Canyon from Oak Glen and Yucaipa. The ridge tapers from a jagged knife-edge at the east end to a rounded series of humps on the lower west end. This trip follows the crest all the way from Galena Peak to Birch Mtn., visiting Little San Gorgonio Peak, Wilshire Mtn., Wilshire Peak, Oak Glen Peak, and Cedar Mtn. along the way. It involves crosscountry travel nearly the entire way, and has some extremely steep and loose sections; despite the relatively short distance, the trip is only suitable for highly experienced navigators who are comfortable moving quickly on difficult terrain. The USGS topographic maps are strongly advisable because they have far more detail than can be shown on a larger scale map. The trip’s difficulty can be reduced somewhat by only doing the section from Galena Peak to Little San Gorgonio Peak, or from Little San Gorgonio Peak to Birch Mtn., but both of these options are still serious undertakings."