Heaven. When it was created, all bills had Adam's face stamped on it. When the holy couple was expelled from the Garden of Edem, which was located somewhere near New England, God gave them as a gift the right to use the currency in a daily basis. After many years, when the Mayflower went to the Garden of Eden, they started to stamp the faces of the presidents that were chosen by Baby Jesus on the dollar bills.
In the future, all currency will have Stephen Colbert's face on it? Why? Because you touch yourself at night. This is expected to increase the value of each ColBuck, as people never, ever, want to part with Colbert.