Layers for the map shown above were compiled from the following sources, which were found using Google:
California state boundary: https://data.ca.gov/dataset/ca-geographic-boundaries
California simple coastline: https://purl.stanford.edu/vx275xn8886
California cities: https://hub.arcgis.com/datasets/cfd2f16171d4422399cd1be936b9e846/about
Major California rivers: https://hub.arcgis.com/datasets/248c535bb8e5404ab987b5178445b7b8/about
Elevation data: https://www.sciencebase.gov/catalog/item/542aebf9e4b057766eed286a