I haven't seen them live but I am old enough to have been already born when this song was released and I remember it because it was one of my all time favorites as a kid. In fact, when I was in 2nd grade I was a latch-key kid and there was this older girl who used to check in on me before my mother got home from work and I asked her to write down the lyrics for me so I could learn them and sing along with it whenever it was played on the radio. And it was played on the radio incessantly throughout the entire decade of '68 through '78.
You're right about Three Dog Night. One of the best groups to come out of that era.