Interesting Things with JC #329: "Mt. Diablo” is one of the most prominent landforms in northern California, located in the San Francisco Bay Area to the east of Walnut Creek. In 1851, it was chosen as the starting point for the Mount Diablo Base Line and Meridian, which were used to measure land in two-thirds of California and all of Nevada. At the top of the mountain, there are amazing views in all directions.