This was written in 1963 by Dino Valenti from Quicksilver Messenger Service. He signed away rights to it when he was imprisoned for marijuana possession. The Youngbloods recorded it and gave the composer credit to Chet Powers, Valenti's real name.
When this was released in 1967, it flopped. It became a hit in 1969 when The National Conference of Christians and Jews distributed it to radio and TV stations to support "Brotherhood Week."
The California group We Five recorded this in 1965. Their version went to US #31.
This song was the last of The Dave Clark Five's eight Top Ten UK hits, reaching #8 when they recorded it as "Everybody Get Together" in 1970. The backing vocals on their version were done by the students of the Central London School of Speech and Drama. Included amongst the backing vocalists was one Peter Davison who went on to star in the BBC TV series All Creatures Great And Small, 1977-79, and as the fifth Dr. Who, 1982-84.