Where's George? is a website that tracks the natural geographic circulation of American paper money.
Users enter the serial number from a bill into the website and that starts the record of where the bill has been.
When the next person who has that bill enters it into the website, the location is updated and everyone who entered the bill is notified.
Is it legal to write on or mark currency?
Where's George? does NOT encourage the defacement of U.S. Currency.
The law defines 'illegal' defacement as defacement that renders bills unfit to be re-issued. For legal details from the the U.S. Bureau of Engraving and Printing, please visit their website.