1996 Map of Mount Day

About this map

Mount Day and Mount Lewis anchor this high-elevation landscape in the Diablo Range, where the county line separates Alameda and Santa Clara counties. The map captures a rugged watershed network where Arroyo Hondo and Alameda Creek carve deep through complex ridge systems like Oak Ridge and Black Ridge. This terrain, largely preserved for conservation and limited access, includes the northern reaches of Joseph D. Grant County Park and Camp Ohlone Regional Park. The presence of Old Camp and New Camp suggests the enduring use of these high flats for seasonal grazing or resource management. Water management is a central theme, evidenced by the Upper Cherry Flat Reservoir and a myriad of named springs that sustain the creeks flowing toward the Arroyo Mocho and beyond.