Cornerstone Community Credit Union (formerly known as Fairfield County FCU) has been open since 1934. It's the 10th largest credit union in Connecticut with assets totaling $49.91 Million and providing banking services to more than 5,000 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.