The Federal Government states that U.S. citizens have over $8 billion in matured U.S. savings bonds. Bonds that are 30 or 40 years old or older, depending on when the bond was purchased, are considered matured savings bonds and do not earn any additional interest.
Below are links which can help you calculate the value of your savings bonds. You will need to know the dollar amount of the bond and the issue date of the bond. If you have the Serial Number of the bond, you can receive more information on the bond as well.