California Mayflower Society aka. The Society of Mayflower Descendants in the State of California is headquartered in Oakland [405 Fourteenth Street, Basement Level]. Of course the national headquarters in located in Plymouth, Massachusetts. They are "...non-profit lineage society dedicated to preserving the history of our Mayflower ancestors through education and research."1 To join, one must prove "...their descendancy from one or more passengers who in 1620 sailed on the merchant ship, Mayflower, from England to what is now Plymouth Massachusetts." The site includes a list of fifty-one passengers on the ship.
http://www.mayflowersociety.com/