Coins of the United States dollar

Coins of the United States dollar (aside from those of the earlier Continental currency) were first minted in 1792. New coins have been produced annually and they make up a valuable aspect of the United States currency system. Today, circulating coins exist in denominations of 1¢ (i.e. 1 cent or $0.01), 5¢, 10¢, 25¢, 50¢, and $1.00. Also minted are bullion (including gold, silver and platinum) and commemorative coins. All of these are produced by the United States Mint. The coins are then sold to Federal Reserve Banks which in turn are responsible for putting coins into circulation and withdrawing them as demanded by the country's economy.
Current coinage.
Today, four mints operate in the United States producing billions of coins each year. The main mint is the Philadelphia Mint, which produces circulating coinage, mint sets and some commemorative coins. The Denver Mint also produces circulating coinage, mint sets and commemoratives. The San Francisco Mint produces regular and silver proof coinage, and produced circulating coinage until the 1970s. The West Point Mint produces bullion coinage (including proofs). Philadelphia and Denver produce the dies used at all of the mints. The proof and mint sets are manufactured each year and contain examples of all of the year's circulating coins.
The producing mint of each coin may be easily identified, as most coins bear a mint mark. The identifying letter of the mint can be found on the front side of most coins, and is often placed near the year. Unmarked coins are issued by the Philadelphia mint. Among marked coins, Philadelphia coins bear a letter P. Denver coins bear a letter D, San Francisco coins bear a letter S, and West Point coins bear a letter W. S and W coins are rarely found in general circulation, although S coins bearing dates prior to the mid-1970s are in circulation. The CC, O, C, and D mint marks were used on gold and silver coins for various periods from the mid-19th century until the early 20th century by temporary mints in Carson City, Nevada; New Orleans, Louisiana; Charlotte, North Carolina; and Dahlonega, Georgia. Most such coins that still exist are now in the hands of collectors and museums.
Bullion coins.
Non-circulating bullion coins have been produced each year since 1986. They can be found in gold, silver, platinum (since 1997), and palladium (since 2017). The face value of these coins is legal as tender, but does not actually reflect the value of the precious metal contained therein. On May 11, 2011, Utah became the first state to accept these coins as the value of the precious metal in common transactions. The Utah State Treasurer assigns a numerical precious metal value to these coins each week based on the spot metal prices. The bullion coin types include "S" (San Francisco, 1986–1992), "P" (Philadelphia, 1993 – 2000), and "W" (West Point, New York, 2001–present).
Commemorative coins.
Modern commemoratives have been minted since 1982. A list is available here.
Mint marks.
List of current and past United States Mint branches and mint marks found on their coins:
Obsolete and canceled coins.
The law governing obsolete, mutilated, and worn coins and currency, including types which are no longer in production (e.g. Indian cents), can be found in .
Note: It is a common misconception that "eagle"-based nomenclature for gold U.S. coinage was merely slang. The "eagle," "half-eagle" and "quarter-eagle" were specifically given these names in the Coinage Act of 1792. Likewise, the double eagle was specifically created as such by name ("An Act to authorize the Coinage of Gold Dollars and Double Eagles", title and section 1, March 3, 1849).
Mill coins.
Although the term mill (also mil or mille) was defined in the eighteenth century as of a dollar or 0.1¢, no coin smaller than 0.5¢ has ever been officially minted in the U.S. However, unofficial mill coins, also called "tenth cent" or "tax-help coins", made of diverse materials—plastic, wood, tin, and others—were produced as late as the 1960s by some states, localities, and private businesses for tax payments and to render change for small purchases.
Legal protections.
The alteration or lightening of U.S. coins for fraudulent purposes is illegal. It is generally legal to melt down coins for the use of their constitent metals, but the Treasury Department has occasionally prohibited melting down and mass exportation when the value of the metal exceeds the face value of the coin. This has happened from 1967 to 1969 for silver coins, from 1974 to 1978 for pennies, and since 2006 for pennies and nickels. The use of elongated coin presses is considered legal because it is not for fraudulent purposes.