In 1690, the Massachusetts Bay Colony became the first government in the Western world to issue paper money. Some of the first counterfeiters of paper money followed soon after. Within a generation, the authorities were engaged in a running battle against forgers, whom they tried to deter by various punishments: cropping their ears, for example, or hanging them. Many colonial notes soon came with a pointed warning: "To counterfeit is DEATH."

Last week, in a ceremony attended by Timothy Geithner and Ben Bernanke, government officials showed off a high-tech $100 bill designed to frustrate 21st-century counterfeiters. It features the pleasing pastels already seen on lesser denominations, as well as a ghostly image of a quill pen and a copper inkwell containing a bell that appears and disappears depending on the angle from which it's viewed. Most startling of all, the front of the bill contains a vertical purple strip that contains shimmering images of the number "100" and the Liberty Bell, all of which miraculously appear to move when the bill is tilted in one direction or another.

With well over a half trillion dollars in "Benjamins" in circulation around the world, the existing $100 bill has attracted the attention of countless counterfeiters. Most have been sophisticated criminal gangs, but there's also a considerable (if controversial) body of evidence linking the most realistic and dangerous counterfeits—the so-called supernotes—with the North Korean government. These twin threats, more than anything else, have driven this latest eye-popping change to our money supply.

If history is any guide, it won't be the last. Paper money in this country has followed a familiar trajectory: new designs, new dollars and, eventually, new counterfeits.

It's perhaps appropriate that Benjamin Franklin appears on the most valuable denomination of dollar in circulation. He designed the country's first money: the Continental dollars issued during the American Revolution to pay the costs of the war. Franklin didn't put his own head on the currency; rather, he used a mysterious anticounterfeiting device he had devised several decades earlier.