1955 Map of Pacheco Pass

About this map

Pacheco Pass serves as the primary corridor through the Diablo Range, bridging the boundary between Santa Clara Co and Merced Co. This 1955 survey, updated in the early 1970s, captures a landscape defined by dramatic elevation changes and a complex network of springs and small lakes. The eastern portion of the map is dominated by the San Luis Reservoir, part of the San Luis Reservoir State Recreation Area, showing the inundation of the valley floor and the resulting shoreline. Away from the water, the terrain is marked by remote landmarks like Whisky Flat and Hagerman Peak. A high density of water sources, including Lucky Spring, Pigs Bath Tub, and Dinosaur Lake, suggests the historical importance of water management for livestock in these upland areas before and after the reservoir's creation.