The United States one-dollar bill ($1), sometimes referred to as a single, has been the lowest value denomination of United States paper currency since the discontinuation of U.S. fractional currency notes in 1876.
Thus the United States moved to a gold standard, making both gold and silver the legal-tender coinage of the United States, and guaranteed the dollar as convertible to 25.8 grains (1.672 grams, 0.05375 troy ounces) of gold, or a little over $18.60 per ounce.