Organizations are required to report abandoned property they have on their books and hold it in trust
Say, for example, you put a security deposit on a flat, but then you suddenly have to move because of something more important, like love or a job offer. Or an old savings account in the bank was accumulating interest on the dime that was left there and finally reached a dollar. Or an insurance premium was charged after you actually cancelled the policy, but nobody noticed. Whenever large organizations find these extra funds they try to return them to their rightful owners, so, technically, they send a letter to the mail address they have on file.
It can take some years for them to figure the rogue twenty dollars are not really theirs, so by the time they try to communicate this situation the owner may very well be gone, to a different state, for instance. At this point the organization has to report the money to the state and pass the money to the treasury. That's the money known as unclaimed.
Normally this data about these funds is provided for free by the local Unclaimed Property Program. In the United States it is the Unclaimed Property division or department within the state treasury that holds the money pretty much forever. The problem is that a) the person doesn't know he or she has unclaimed money, so she or he just doesn't check the government resources and b) too often people forget to check information from all states they ever lived in. This way some accounts have been unclaimed since the seventies, and will, possibly, never be claimed.
This website is one of the few free services that help people find their unclaimed property across many places at once. We provide information about private unclaimed accounts, organized alphabetically by the name of the person who is owed the money.