The process by which the Mint makes coins has advanced greatly since 1792. The first Philadelphia Mint used harnessed horses to drive the crude machinery that produced our coinage. The manual process required heating of metals in a blacksmith-like furnace, and flattening them into sheets by repeated trips through rollers. Coin shapes were then punched out of the metal sheets, and these were hand-fed into machines that stamped on coin faces. The coin making process was a physical and tedious one and imperfect coins were frequent.
Today, the Philadelphia and Denver Mints—which employ a highly-automated version of the same based steps used in 1792—often produce millions of coins for circulation in 24 hours. The modern Philadelphia and Denver facilities together in recent years have produced as many as 28 billion coins in a single year.
In the Act of 1792, Congress mandated that all American coins show on one side "an impression emblematic of Liberty, with an inscription of the word Liberty, and the year of coinage; and upon the reverse of each of the gold and silver coins shall be the representation of an eagle, with this inscription, 'UNITED STATES OF AMERICA'. . . " Many changes in coin designs have been made since 1792; however, much from the original design scheme remains.
In 1899, Washington's image was placed on a U.S. commemorative coin, the Lafayette dollar. Ten years later, a circulating coin, the Lincoln cent, was issued to commemorate the 100th anniversary of his birth. In 1932, Washington appeared once again on a U.S. coin, the quarter, and still does today. Thomas Jefferson's image appeared on the nickel six years later.
In 1946, soon after Franklin D. Roosevelt's death, the Mint issued the FDR dime, which commemorated his ardent support of the March of Dimes. The John F. Kennedy half dollar was adopted in 1964, just months after his assassination.
Public Law 95-447, dated October 10, 1978, provided for the issuance of the Susan B. Anthony dollar. Placement of Susan B. Anthony's likeness on the new dollar represented the first time that a woman, other than a mythical figure, appeared on a circulating coin.
And the Dollar Coin Act of 1997, Public Law 105-124 dated December 1, 1997, provided for a new dollar coin to be placed into circulation when supplies of the Susan B. Anthony dollar coin were exhausted. This coin honored Sacagawea, the young Shoshone woman who provided critical assistance to the Lewis and Clark expedition. It was first issued in 2000.
The 1792 law directed American money to be made of gold, silver and copper in denominations of $10, $5 and $2.50 pieces. The dollar, half-dollar, quarter, dime and half-dime were composed of silver. The cent and half-cent were made of copper.
Minting from gold and silver continued well into the 20th century. It was not until 1933, during the Great Depression, that the Mint ceased producing gold coins. A silver crisis caused the replacement of silver in 1966 in quarters and dimes; however, the half-dollar was composed of 40 percent silver from 1965 to 1970. The Bicentennial Kennedy Half Dollar contained 80 percent silver and 20 percent copper. But today these coins are now composed of cupro-nickel clad, with a pure copper core, and an outer layer of a 75 percent copper, 25 percent nickel alloy.
Nickels are made from the same 75-25 alloy, and the cent, once a copper coin, is now composed of copper plated zinc. The cents are less expensive for the Mint to manufacture, and at 2.5 grams each weight about 20 percent less than cent previously minted of 95 percent copper and 5 percent zinc, which weighed 3.11 grams. The cent's composition was changed in 1982, and cents, and both copper and copper-plated zinc cents were produced that year.