Code for America
Code for America is an organization with chapters all over the United States. As of 2022, it seems to attract data nerds.
Code for San Francisco
Code for San Francisco is a much smaller non-profit that is vaguely affiliated with Code for America. It's an all-volunteer organization, for which sometimes Code for America employees volunteer to help out with (if for no other reason than to keep other volunteers from trashing their conference rooms and desks).