CASSIDI: from Federal Reserve of St. Louis allows to search for and view banking market definitions, find banking market concentrations and perform "What If" (pro forma) HHI analysis on banking market structures.
FDIC: provides wealth of information on banking industry. See Bulk Download Site for summary of deposit data.
WRDS: ChooseBank Suite by WRDSto access accounting data for bank holding companies, commercial banks, savings banks, and savings and loans institutions.It also includes raw call report data from the FFIEC and bank holding company financials and structure data from the NIC on an ongoing basis. Legacy Bank Regulatory provides similar data from the Federal Reserve Bank of Chicago which stopped updating data in 2021.