Son of Wilton and Ethel (née Duncan) Gregory. Convert to Catholicism at age 11, he was drawn to the priesthood before joining the Church. Studied at Archbishop Quigley Preparatory Seminary, Niles College, and Saint Mary of the Lake Seminary. Ordained on 9 May 1973 in the archdiocese of Chicago, Illinois. Received a Doctorate in Sacred Liturgy from the Pontifical Liturgical Institute in Rome, Italy in 1980. Taught at Saint Mary of the Lake Seminary. Master of Ceremonies for Cardinal John Cody and Cardinal Joseph Bernardin. Auxiliary Bishop of Chicago and Titular Bishop of Oliva on 31 October 1983. Bishop of Belleville, Illinois on 29 December 1993. President of the United States Conference of Catholic Bishops from 2001 to 2004. Archbishop of Atlanta, Georgia on 9 December 2004. In 2007 he was diagnosed with and operated on for prostate cancer.