San Diego County Credit Union has been open since 1938. It's the 5th largest credit union in California and the 12th largest in the United States with assets totaling $8.4 Billion and providing banking services to more than 412,000 members. Membership: The credit union is a member-owned financial cooperative providing banking services including savings, loans, and other financial services to members. Membership is also open to immediate family of current members.