On July 5, 1978, Murphy was appointed bishop of the Diocese of Great Falls-Billings by Pope Paul VI; he was consecrated by Archbishop Cornelius Power on August 21, 1978.[4][5] In 1979, Murphy addressed the National Catholic Education Association on vocations to the priesthood and their on the importance for the local church.[2]
Coadjutor Archbishop of Seattle
On May 26, 1987, Pope John Paul II appointed Murphy as coadjutor archbishop of the Archdiocese of Seattle, with immediate right of succession to Archbishop Raymond Hunthausen. Murphy's appointment came after a series of controversies surrounding Hunthausen, first prompted by an apostolic visitation to the archdiocese ordered by then Cardinal Joseph Ratzinger, prefect of the Congregation for the Doctrine of the Faith. Ratzinger was concerned about Hunthausen violating church doctrine. On December 3, 1985, the pope appointed Reverend Donald Wuerl as auxiliary bishop of Seattle, with authority to overrule Hunthausen in several important areas.[6] After protests from Hunthausen and other American prelates, Pope John Paul II removed Wuerl and appointed Murphy as a coadjutor archbishop with less immediate authority.[6]
Archbishop of Seattle
Murphy automatically became archbishop of the Archdiocese of Seattle upon Hunthausen's retirement on August 21, 1991. As archbishop, Murphy traveled extensively to parishes around the archdiocese and was an advocate for the poor and disenfranchised. He oversaw an extensive renovation of St. James Cathedral, which was completed in 1994. Under Murphy's administration the archdiocese saw an increase in registered Catholics, and an increase in outreach and ministries for women, various ethnic groups, and LGBT individuals.[7]
In 1992, Murphy opened Elizabeth House in Seattle, which provided medical and job training for pregnant teens.[8] For small Washington towns that were suffering from cutbacks in the timber industry, Murphy provided $500,000 to assisting starting small businesses. To help offset the declining numbers of priests, he provided financial support to a Seattle University program to train lay people in assist in some parish duties.
In 1999, Holy Cross High School, a Catholic school in Everett, Washington, was renamed Archbishop Thomas J. Murphy High School in his honor.[2] In 2000, a new organ built in the apse of St. James Cathedral was named the Archbishop Thomas J. Murphy Millennium Organ. The "Archbishop Thomas J. Murphy Memorial Parish Stewardship Award" is named in his honor.[11]
In 2006, the archdiocese dedicated the Archbishop Murphy Courtyard on the south side of the cathedral. It contains a fountain and pool, a marker stone and a statue of Mary, mother of Jesus.[12]