UC Davis School of Law Professor Gabriel “Jack” Chin leads a research project on Chicago Cafe as the oldest operating Chinese restaurant in California and perhaps even the United States. The restaurant began serving customers in 1910, though its origins could stretch back to 1903. Andri Tambunan for The Guardian.
https://www.theguardian.com/environment/2024/may/02/oldest-chinese-american-restaurant-chicago-cafe