In an effort to improve the security of the monetary system, the Bureau of Engraving, the Secret Service ... issues dollar bills in seven denominations: $1, $2, $5, $10, $20, $50, and $100.

Artist Dan Tague has found hidden messages encrypted in U.S. dollar bills. He would fold a dollar bill as many as 100 times to come up with phrases made up by the letters on the money. Tague's ...