The 1964 half dollar was the first year the Kennedy half dollar. The 1964 Kennedy half dollars were also the last year of issue for the 90% silver half dollar. After that from 1969-1970 the half dollar had 40% silver composition and by 1971 silver was removed completely.
Because of their silver content, these coins make an excellent investment and will hedge your earnings against inflation. Visit my site for more information on all silver half dollars.