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 held its first official Board Meeting on December 7, 1932 and its first annual meeting on January 14, 1933. As of December 31, 1932, Firstmark Credit union had a total of 40 members. Total assets were $475 and total loans were $300. Firstmark had a total of 5 borrowers. The Credit Union was first located at Fox Tech High School until 1947 when it moved to the San Antonio Teachers Council on Adams Street. Those facilities were outgrown in 1966 and the office was moved to 303 South Santa Rosa Street in downtown San Antonio where it remained for fourteen years. Then, in May 1980, the move to the location at 10730 Gulfdale took place. The Credit Union's first branch office opened in July 1986 on the city's south side at 2327 S. W. Military Drive.

In 2013, Firstmark Credit Union acquired Southside Credit Union to develop and strengthen their relationships with members throughout south San Antonio. Firstmark gained 3 additional financial centers branches through the expansion. Additionally, Firstmark acquired St. Joseph’s Credit Union in 2015, expanding Firstmark’s member base and helping the credit union achieve over $1 billion in assets. St. Joseph’s Credit Union was originally chartered in 1933 to support the catholic communities in San Antonio, Del Rio, and Fredericksburg. With both mergers, members of these communities were able to take advantage of the expanded products and services available, technology, and larger ATM network that Firstmark provides. There are several additional ways a non-member can qualify for membership at Firstmark Credit Union. Visit any one of our 11 financial centers to explore other ways you may be eligible. Firstmark Credit Union has operated continuously since 1932 and we have endeavored to serve everyone in our field of membership with prompt, efficient and personal service. Because of our efforts to provide dependable, courteous service, the Credit Union has established long-term relationships with loyal members who depend on the Credit Union to fulfill their financial needs.