The ten-dollar bill is a denomination of United States currency. It features a portrait of Alexander Hamilton, one of the Founding Fathers and the first Secretary of the Treasury. The bill is primarily blue and has various security features, including a security thread and color-shifting ink. The current design of the ten-dollar bill was introduced in 2006. It includes images of the U.S. Capitol on the back, along with a depiction of Hamilton's signature. The bill is commonly used in everyday transactions and is an important part of the U.S. monetary system.