Firstmark Credit Union Firstmark Credit Union (Formerly San Antonio Teachers Credit Union) is a member-owned, locally controlled, not-for-profit financial cooperative. It was chartered in 1932, giving it the honor of being the oldest state-chartered credit union in San Antonio, Texas.         Firstmark Credit Union Service Telephone Member Care Center: 210.442.0100 800.683.1211 (Toll-Free) Loan Application Line: 210.442.0199 Online Banking Login How to Log In 1. Visit the bank’s website https://www.firstmarkcu.org/.     2.  The Login is located to the…