Dollar bills are paper currency used in the United States, representing various denominations, including $1, $5, $10, $20, $50, and $100. They are issued by the U.S. Department of the Treasury and feature distinct designs, colors, and security features to prevent counterfeiting. Each bill has a portrait of a notable figure, such as George Washington on the $1 bill and Abraham Lincoln on the $5 bill. Dollar bills are widely accepted for transactions and can be used to purchase goods and services. They are also a part of the Federal Reserve System, which manages the country's money supply. The physical design of dollar bills has evolved over time, with the most recent redesigns incorporating advanced security measures.