Helena, Mont. ? The federal government is facing a lawsuit over billions in unclaimed bonds that date back to the patriotic fundraising efforts of World War II, leading to a showdown between states who say they should be given the money and a Treasury Department that claims ownership.

World War II sparked an unprecedented bond buying campaign, spurred on by one of the largest advertising campaigns ever seen — a drive wrapped in dutiful pleas from celebrities, politicians and cartoon characters alike.

Most American families bought at least one bond at the time and many never cashed them in — thanks in part to a 40-year maturity in the bonds. And those same “Series E” war bonds continued to be sold by the federal government until 1980.

More than $16 billion worth of the bonds are unclaimed, either lost or forgotten about with the death of the original purchasers.

The state attorneys general suing the Treasury Department charge that the federal government made no effort to find those people. They want the money given to the states, who have a legal system in place for finding the owners of unclaimed funds.

The Treasury Department counters that it indeed tries to find owners of the unclaimed bonds, and says it has a Web site where people cam simply type in their Social Security number to see if they have one.

The Treasury also points out that most of the unclaimed bonds are far more recent than the original World War II era bonds. And overall, 99 percent of people claim their bonds.

And those who don’t cash them often choose to do so for tax reasons, or perhaps out of a sense of patriotism.