United States, California, Contra Costa, Mount Diablo State park, Fossil Ridge, just upslope of South Gate Rd., just west of Gibraltar Rock, southeast of Rock City. T01S R01W S13 SW1/4
Other oaks growing in the area: Q. lobata, Q. douglasii, Q. agrifolia, Q. kelloggii, and Q. chrysolepis. This tree next to Dean 655, actually collected by B. Ertter (label has Dean as primary collector).
Label says: J.M. Tucker and Beecher Crampton Herbaria; The UC Davis Herbarium.