The eagle was a United States $10 gold coin issued from 1792 to 1933.
The eagle was the largest of the five main decimal base-units of denomination used for circulating coinage in the United States prior to 1933, the year when gold was withdrawn from circulation. These five main base-units of denomination were the mill, the cent, the dime, the dollar, and the eagle, where a dime is 10 cents, a dollar is 10 dimes, and an eagle is 10 dollars. The eagle base-unit of denomination served as the basis of the gold quarter-eagle (US$ 2.50), the gold half-eagle (US $5), the eagle (US $10), and the double-eagle coins (US $20).
With the exceptions of the gold dollar coin, the gold three-dollar coin, the three-cent nickel, and the five-cent nickel, the unit of denomination of coinage prior to 1933 was conceptually linked to the precious or semi-precious metal that constituted a majority of the alloy used in that coin. In this regard the United States followed long-standing European practice of different base-unit denominations for different precious and semi-precious metals. In the United States, the cent was the base-unit of denomination in copper. The dime and dollar were the base-units of denomination in silver. The eagle was the base-unit of denomination in gold although, unlike "cent", "dime" (or "disme"), and "dollar", gold coins never specified their denomination in units of "eagles". Thus, a double eagle showed its value as "twenty dollars" rather than "two eagles".