Many of the most popular U.S. coins were struck in silver.  Silver coins were what the United States Mint mainly produced and are very popular to coin collectors.   Many denominations of silver coins have been struck including the three-cent piece, silver half-dime, twenty-cent piece, quarter dollar, half dollar, and the one dollar coins.  All these coins brought some importance to the economic structure of the United States.  Silver coins were without a doubt one of the most regarded collectible coins minted by the United States Mint.