Photos taken on April 2, 2019 in Pinole (San Francisco Bay Area), California.
Cassin's would be an unusual bird for this area, but compared to a Purple Finch, this bird seems to have a less distinct facial pattern, relatively dark, crisp, and sparse streaking, a longer bill and a STRAIGHT culmen. (House finch would have virtually no facial pattern, more diffuse, browner streaking, and smaller bill with curved culmen.)
Thanks in advance, Jack