Mid-Atlantic Federal Credit Union has been open since 1968. It's the 20th largest credit union in Maryland with assets totaling $319.29 Million and providing banking services to more than 25,000 members. Membership: The credit union is a community-based financial institution. People living, working, or worshipping in the credit union's geographic area can become a member and access banking services. Membership is also open to immediate family of current members.