The US had expected the American casualties in World War II to be much greater than they ultimately were. In preparation for the invasion of Japan, Operation Downfall, some 1,506,000 Purple Hearts were made. Though Operation Downfall was abandoned when Japan surrendered after the bombs were dropped on Hiroshima and Nagasaki, the Purple Hearts made for it are still being used today. Most of these Purple Hearts have been issued.
As of June 5 2010, a staggering 1,910,162 have been issued. Interestingly, around 120,000 more are circulated through the present armed forces, so that they can be awarded without delay. Everything else from World War II (tanks, bullets, k rations), has since been used, sold, or scrapped, but the Purple Hearts made for our Great Grandfathers are still being pinned on our soldiers today. You can read more at the source