Mint marks are letters that identify where a coin was made. They hold the maker responsible for the quality of a coin. When the U.S. used precious metals such as gold and silver to make circulating coins, a commission evaluated the metal compositions and quality of coins from each of the Mint facilities. The evaluations ensured that each facility produced coins to the correct specifications.
Philadelphia was the only branch in operation in the Mint’s earliest years, so identifying the sources of a coin was not necessary. A March 3, 1835 Congressional Act established mint marks in the United States, along with the first Mint branches. When the Mint branches in Charlotte, Dahlonega, and New Orleans opened in 1838, mint marks made their first appearance on U.S. coins. However, the practice of not identifying Philadelphia’s coins continued even after the first branches were established.
This changed in 1942. When nickel was removed from five-cent coins during World War II, the “P” mint mark first appeared on coins produced in Philadelphia. The mark’s position also moved from the right of Monticello to above the dome to indicate the new metal composition. After the war, when use of the regular alloy resumed, the mint mark returned to its former position and the Mint no longer used Philadelphia’s “P.”
In 1979, the Susan B. Anthony dollar coin was introduced. Once again, the “P” mint mark appeared. The following year, the “P” appeared on all of the denominations except the cent, which still holds true today.
The table below lists the mint marks for each of the Mint’s current and historic facilities, and the dates they used the mark.
The Mint adds mint marks to the master hub, the first stage of the die making process. The Philadelphia Mint makes a master hub for each facility that will strike the coin.