On October 28, 1965, Berrigan, along with the Rev. Richard John Neuhaus and Rabbi Abraham Joshua Heschel, founded an organization known as Clergy and Laymen Concerned About Vietnam (CALCAV). The organization, founded at the Church Center for the United Nations, was joined by the likes of Dr. Hans Morgenthau, Dr. Reinhold Niebuhr, Rev. William Sloane Coffin, and the Rev. Philip Berrigan, among many others. The Rev. Dr. Martin Luther King Jr., who delivered his 1967 speech "" under sponsorship from CALCAV, served as the national co-chairman of the organization.