After twenty years the account no longer exists if it was just a straight bank account. If it was an investment or brokerage account and there was something in it then it would still be active, however checking accounts would not be.
Funds from dormant accounts are turned over to the state. You will have to contact your state financial regulation department ( listed in your phone book ) and connect to the unclaimed funds department.
You can only access any funds if you have a will designating you as the beneficiary however. If you don't the state keeps the funds.