Peter Yarrow, one-third of the folk trio Peter, Paul and Mary, has died at the age of 86. Yarrow's death was confirmed by his publicist, who stated that he had been battling bladder cancer for the past four years. Alongside Noel Paul Stookey and Mary Travers, Yarrow helped establish Peter, Paul and Mary as one of the most popular folk acts of the 1960s. The group achieved success with hits like 'If I Had a Hammer' and 'Puff the Magic Dragon.' Yarrow also wrote and co-wrote many of the group's songs, and they were known for their progressive politics and support of civil rights causes.