Silver dollars were discontinued in 1935. Half dollars, quarters and dimes were minted with a 90% silver alloy through 1964. While quarters and dimes went to a copper-nickel clad composition, half dollars used a 40% silver alloy through 1970.
Since 1970, there have been several coins produced with silver content. They were made for collectors' annual proof sets and not for general circulation. The Bicentennial Half Dollar, minted in 1975 and 1976, was made in both 80% silver and copper-nickel clad. Eisenhower dollars, from 1971 through 1974, had 40% silver versions. The U.S. Mint has produced silver coins for annual silver proof sets since 1992, according to NumisMaster.com.