The "eagle", "half eagle", and "quarter eagle" were specifically given these names in the Act of Congress that originally authorized them ("An act establishing a mint, and regulating coins of the United States", section 9, April 2, 1792). Likewise, the double eagle was specifically created as such by name in the Coinage Act of 1849 ("An act to authorize the coinage of gold dollars and double eagles", title and section 1, March 3, 1849). Prior to 1850, eagles with a denomination of $10 were the largest denomination of US coin. The $10 eagles were produced beginning in 1795, just two years after the first U.S. mint opened. Since the $20 gold piece had twice the value of the eagle, these coins were designated "double eagles".
The first double eagle was minted in 1849, coinciding with the California Gold Rush. In that year, the mint produced two pieces in proof. The first resides in the Smithsonian Institution in Washington, D.C.. The second was presented to Treasury Secretary William M. Meredith and was later sold as part of his estate—the present location of this coin remains unknown.
In 1904, President Theodore Roosevelt sought to beautify American coinage, and proposed Augustus Saint-Gaudens as an artist capable of the task. Although the sculptor had poor experiences with the Mint and its chief engraver, Charles E. Barber, Saint-Gaudens accepted Roosevelt's call. The work was subject to considerable delays, due to Saint-Gaudens's declining health and difficulties because of the high relief of his design. Saint-Gaudens died in 1907, after designing the eagle and double eagle, but before the designs were finalized for production. The new coin became known as the Saint-Gaudens double eagle.
Regular production continued until 1933, when the official price of gold was changed to $35/oz by the Gold Reserve Act. The 1933 double eagle is among the most valuable of U.S. coins, with the sole example currently known to be in private hands selling in 2002 for $7,590,020.
According to wikipedia