I’m just going to quote the description that MrHaagsesjonny1, who posted this to YouTube, attached to the video, because it says everything I’d say about the song and The 5th Dimension:
In 1969, The 5th Dimension peaked for 6 week at No.1 on the US Billboard Hot 100 chart with “Aquarius / Let The Sunshine In.”
For lyrics, see below. The song with it’s uplifting, elegance and tremendous harmonies, is a combination of two songs written for the 1967 iconoclastic musical Hair by James Rado and Gerome Ragni (lyrics), and Galt MacDermot (music). The single was eventually certified platinum in the U.S. Instrumental backing was provided by the Wrecking Crew, and the song listed at No. 66 on Billboard’s “Greatest Songs of All Time.”
The 5 original 5th Dimension members were (in the video):
Billy Davis Jr.(lead singer), Marilyn McCoo (brown hair), Florence LaRue, Lamonte McLemore (yellow shirt), and Ronald Townson (68, † August 2, 2001 – He performed right up until kidney illness forced him to retire in 1997).
The group has a star on the Hollywood Walk of Fame, inducted August 9, 1991. And was inducted into the Vocal Group Hall of Fame in 2002.