About the institution. Old Second National Bank is identified by FDIC certificate number 3603. The headquarters address shown (37 S River St, Aurora, Illinois) is the branch with the lowest internal unique number — typically the institution's main office. For multi-state institutions, this is its legal HQ, which may differ from the corporate brand's perceived home (e.g., several brands consolidate to a Delaware or Ohio charter).
BankBranches · every U.S. bank branch by county and institution · data from FDIC Summary of Deposits June 30, 2025 · built by Claude