When did they stop making all silver half dollars?

Half dollars have never been made out of pure silver but all half dollars minted before 1965 are 90% silver, halves dated 1965-1970 are 40% silver. Circulation issue halves dated 1971 and later are copper nickel and thus worth 50 cents. The US still makes commemorative half dollars such as the 90% silver proof half dollars made from 1992-present.