The short answer is inheritance happens. If there's no co-signers, named beneficiaries, will or heirs, the state will eventually appoint an executor who will settle any outstanding debts of the estate against the account, and then I think the state itself is the ultimate inheritor.
Most states have a notion of "unclaimed funds", and you can check to see if you have any money sitting in the state coffers from a dead relative or a settlement.
I'll add to that the issue that it's extremely unlikely for there to be no heirs, as even if you made no family and your parents are dead, there's still likely to be e.g. some third-degree cousins. There are some cases (e.g. related to the Holocaust or immigrants where all the local family is dead and there are no contacts with the overseas relatives) but generally there's quite some time for distant relatives to apply until eventually the state (i.e. the general public) takes it over.
The short answer is inheritance happens. If there's no co-signers, named beneficiaries, will or heirs, the state will eventually appoint an executor who will settle any outstanding debts of the estate against the account, and then I think the state itself is the ultimate inheritor.
Most states have a notion of "unclaimed funds", and you can check to see if you have any money sitting in the state coffers from a dead relative or a settlement.