What years weren't silver dollars minted?

As far at the 20th Century, there were no silver dollars minted 1905-20, 1929-33, and 1936-1970. The Eisenhower dollar was minted 1971-78, but it was mostly copper instead of silver. Following that was the Susan B. Anthony dollar, which was much smaller, also made of copper/nickel instead of silver, minted 1979-81 and 1999.