Why US Dollar Bills Were Printed Green
In the 1860s, the US government issued paper Demand Notes to fund the Civil War. Officials chose green ink for the reverse side specifically because nineteenth-century cameras could only take black-and-white photos. Counterfeiters had been photographing paper banknotes and using the resulting plates to print fakes, but the patented green tint could not be chemically stripped or photographed cleanly. The anti-counterfeiting ink worked so well that green remained the standard.
The Wild Era of Unregulated Paper Currency
Before the American Civil War, the United States had no unified national paper currency in daily circulation. The federal government minted gold and silver coins, but paper money was issued by hundreds of state-chartered, private commercial banks. Each institution designed, engraved, and printed its own distinct banknotes, resulting in thousands of different note varieties circulating simultaneously across the country.
This fragmented monetary system created an ideal environment for fraud. Because merchants and citizens could not possibly recognize every legitimate banknote design among the thousands in circulation, counterfeiters flourished. Fraudulent printers altered genuine low-value notes to look like higher denominations, produced entirely fictitious bills from non-existent banks, or copied legitimate designs onto inferior paper, severely undermining public confidence in paper money.
The Rise of Photographic Counterfeiting
By the 1850s, the advancement of early photography introduced an unprecedented threat to paper currency. Mid-nineteenth-century cameras operated strictly in monochrome, capturing images through black-and-white plates. Counterfeiters realized that if a banknote was printed purely in black ink on white paper, it could be photographed directly with remarkable clarity and precision.
Once a criminal had captured a clean photographic negative of a banknote, they could expose the image onto a sensitized metal plate, etch the lines, and mass-produce nearly undetectable counterfeit bills using a standard printing press. Furthermore, existing colored inks of the era were vulnerable to chemical stripping; counterfeiters used acids and solvents to wash away face values and overprint larger denominations without damaging the underlying paper base.