220px-The_5th_Dimension_-_The_Age_of_Aquarius#9– The 5th Dimension – “Aquarius/Let The Sunshine In” – (1969)

This is one of those songs that just screams “1969.” It’s actually a medley of two songs written for the Broadway musical Hair and it was a #1 hit in 1969. It’s pretty fantastic all around, from the vocal harmonies to the musicianship.