アメリカ合衆国1ドル硬貨はいつから発行が終わった？
The dollar coin is a United States coin worth 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 1.043 inches (26.5 mm) and a thickness of .079 inches (2 mm), 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. The term silver dollar is often used for any large white metal coin issued by the United States with a face value of one dollar, whether or not it contains some of that metal. While true gold dollars are no longer minted, the Sacagawea and Presidential dollars are sometimes referred to as golden dollars due to their color. 
1794