The Federal Deposit Insurance Corporation (FDIC)
Before the creation of the Federal Deposit Insurance Corporation (FDIC) in 1933, bank accounts were anything but secure. In the 1920s and 1930s, thousands of U.S. banks went belly up and took people's life savings with them [source: FDIC]. President Franklin D. Roosevelt created the FDIC to provide much-needed stability to a financial system mired deeply in the Great Depression.
The agency insures all deposits in FDIC-insured banks up to $250,000 per account. If a bank fails — or is closed by government regulators — the FDIC is responsible for distributing all remaining funds and settling all insured accounts. It's possible that you or a close relative had money in a failed bank and never received your check from the FDIC.
Plug your name into the FDIC database and see what comes up. You should be aware, though, that as of this writing (2014) the FDIC is only processing payments for institutions that failed between 1989 and 1993, the era of the savings and loan crisis, or undelivered or uncashed dividend checks [source: FDIC].