With the passage of the Native American $1 Coin Act on September 20, 2007, the U.S. Mint began designing a series of Sacagawea dollars with modified reverses to further commemorate "Native Americans and the important contributions made by Indian tribes and individual Native Americans to the development of the United States and the history of the United States". Four designs were to be minted, each for one year from 2009 to 2012. The first Native American series coin was released in January 2009 and had a reverse that depicted a Native American woman sowing seeds of the Three Sisters, symbolizing the Indian tribes' contributions to agriculture.