What year did quarters stop being made of silver?

1964 was the last date for 90% silver quarters and dimes. The composition was changed to copper-nickel in 1965, when the price of silver soared over the face value of the coins.

Note that halves were made out of 40% silver for 6 more years. Also, contrary to popular myth, pre-1965 nickels were NOT made of silver, except for the famous war nickels made during 1942-45.