Area code 904 serves the northeastern corner of Florida, including Jacksonville, St. Augustine, and Orange Park. Originally created in 1965 and later restricted to its current area after multiple splits, it is now overlaid by 324, with ten-digit dialing required. Jacksonville, Florida’s most populous city, anchors the region with a strong presence in banking, military, logistics, and healthcare. Area code 904 remains one of Florida’s most recognized codes, deeply tied to Jacksonville’s growth, coastal access, and cultural influence in the state’s northeast.