The dollar coin is a United States coin with a face value of one United States dollar. It is the second largest U.S. coin currently minted for circulation in terms of physical size, with a diameter of and a thickness of , coming second to the half dollar. Dollar coins have been minted in the United States in gold, silver, and base metal versions. Dollar coins were first minted in the United States in 1794. While true gold dollars are no longer minted, the Sacagawea, Presidential, and American Innovation dollars are sometimes referred to as golden dollars because of their color.