Blowin' in the Wind
It is a premier example of the protest song, posing as it does philosophical questions about peace, war and freedom. Its popularity and timelessness can perhaps be attributed to the fact that while the song asks these questions, it does not refer specifically to any particular political event (such as the Vietnam War, which was almost certainly one of the inspirations for the lyrics).
It has been covered by literally hundreds of artists. Just a few of the better-known acts who have done so are folk music trio Peter, Paul and Mary (who actually released their version a few months before Dylan); country guitar virtuoso Chet Atkins; folk chanteuse Judy Collins; soul singer Sam Cooke; blues belter Etta James; Elvis Presley; and Stevie Wonder.