Not an icon for the past 20 or so years but Mary had a wonderfully low voice for a woman and Paul Stookie and Peter Yarrow became quite accomplished at harmonizing around her. "Puff" is probably their best known song although, in their Greenwich Village days, hanging around with a bunch of unknown (but soon to be well known) artists and musicians, Dylan was the poet/composer of choice, and they were quite radical in their politics.
John Sebastian was a friend in those days, as was John Phillips, later of the Mamas and the Papas. The song that catapulted Peter, Paul & Mary onto the pop charts (they liked the money but that was about all) was "Leavin' On a Jet Plane" written by John Denver. Sometime around 1970, Peter Yarrow got married and Paul wrote the "Wedding Song" which I played at countless weddings in the 1970's.
Their concerts, particularly their reunion concerts in the 1980's and 1990's and later, were quite enjoyable and often quite spontaneous. I saw them in Syracuse and had the chance to talk for a few minutes with Peter Yarrow. They were pretty comfortable by then and only did concerts for some cause. In Syracuse, there was an effort to rehab a beautiful old vaudeville theatre and they donated most of their proceeds. There were always rumors about Mary having an affair with one or the other (Peter or Paul) and she always categorically denied it with grace and certainty. May this great lady rest in peace.