Overview
Mastercard runs a large technology and operations campus in O'Fallon that helps process card transactions worldwide.
History
The campus opened in the 2000s and has grown into one of the region's major technology employers.
Today
Secure technology campuses like it need strict access control and facility security.
Compiled October 2026. History is summarized for general interest; check primary sources for research. This landmark is local context, not an employer or job listing.