From May of 1973 (cue the laughter):
Unlike @ImJustKCClone, I chose the #1 R&B song from that year:
Others I always associate with that time:
Crocodile Rock by Elton John
Angie by the Stones
We're An American Band by Grand Funk Railroad
Also, add America, by Simon & Garfunkel to your "others" list. It came out in late 72, so it was during our senior year.