Cardinal William Henry Keeler, Archbishop emeritus of Baltimore (USA), was born on 4 March 1931, in San Antonio, Texas, the son of Thomas L. Keeler and Margaret T. (Conway) Keeler. He was raised in Lebanon, Pennsylvania, where he attended St Mary School and Lebanon Catholic High School. He received a B.A. from St Charles Seminary in Overbrook, Philadelphia, in 1952 and a Licentiate in Sacred Theology from Pontifical Gregorian University in Rome, in 1956.

Ordained a priest on 17 July 1955, in the Church of the Holy Apostles, Rome, by Archbishop (and future Cardinal) Luigi Traglia, the young cleric became assistant pastor at Our Lady of Good Counsel Church, Marysville, and secretary of the diocesan Tribunal (1956-58). He was then assigned to study Canon Law at the Pontifical Gregorian University in Rome. In 1961, he received his doctorate in Canon Law and was reappointed by Bishop George L. Leech as assistant pastor of Our Lady of Good Counsel Church and defender of the bond of the diocesan Tribunal. In 1964, he was named pastor of the Marysville parish.

As secretary to Bishop Leech during the Second Vatican Council meetings in Rome (1962-1965) he was appointed peritus or 'special advisor' to the Council by Pope John XXIII. During the Council, he also served on the staff of the Council Digest, a daily communication service sponsored by the United States Bishops. At the close of the Council in 1965, he was named Papal Chamberlain, with the title of Monsignor, by Pope Paul VI. In 1970, he was named Prelate of Honor by Pope Paul VI.

In 1965 he was appointed to serve as Vice Chancellor of the Harrisburg Diocese and, in time, Chancellor (1969) and later Vicar General. He held the latter position when he was appointed Auxiliary Bishop of Harrisburg and Titular Bishop of Ulcinium (Dulcigno) by Pope John Paul II on 24 July 1979. His episcopal ordination occurred on 21 September 1979, at St Patrick Cathedral, Harrisburg.

On 3 September 1983, he was elected Administrator of the Diocese of Harrisburg by the College of Consultors. Pope John Paul II appointed him Bishop of Harrisburg on 10 November, 1983, and he was installed as Bishop on 4 January 1984, by His Eminence, Cardinal John Krol, Archbishop of Philadelphia.

On 1 September 1989 he was appointed to the Board of Trustees for the Catholic University (four year term); on 1 March 1993: he was appointed to the Advisory Panel for the Father Michael McGivney Fund for New Initiatives in Catholic Education (one year term).

He was appointed Archbishop of Baltimore, United States of America, by Pope John Paul II on 6 April 1989, and was formally installed as 14th Ordinary of the nation's oldest see on 23 May in ceremonies at the Cathedral of Mary Our Queen. 

An influential participant in national and international issues involving the Church Archbishop Keeler was elected President of the National Conference of Catholic Bishops (NCCB) in November 1992 until 1995. He had been elected as the organization's Vice-President in November of 1989, when he hosted Baltimore's bicentennial celebration of the founding of America's first Roman Catholic Diocese.

As part of his work with the NCCB, Archbishop Keeler has developed a reputation for effectively building interfaith bonds. He is particularly noted for his work in furthering an effective Catholic-Jewish dialogue and served for a time as moderator of religious relationships with Jewish faith. As chairman of the NCCB's Committee for Ecumenical and Interreligious Affairs from 1984 to November 1987, he helped arrange the Pope's meetings with Jewish leaders in Miami and with Protestant leaders in Columbia, S.C., during the 1987 Papal Visit. After being elected President of the national organization, Archbishop Keeler said his top two priorities for the organization would be helping to energize the Church's efforts in evangelization and in education. The Archbishop was appointed to the Pontifical Council for Promoting Christian Unity in the Fall of 1994.

In addition to promoting the value of Catholic education, one of Archbishop Keeler's priorities as leader of the oldest Catholic See in the United States has been to voice the need for moral instruction as part of the education process of all students. He also has been a vigilant leader of the pro-life movement and an outspoken advocate for expanded evangelization throughout the parish community. Upon arriving in Baltimore, Archbishop Keeler quickly began bolstering the historic Archdiocese's educational and social outreaches and pastoral programs for the Church. Housing opportunities have been expanded for many of central and western Maryland's homeless; tuition assistance has been increased for families; parishes have received assistance for hiring youth ministers; access ramps and lifts were installed at many Churches; and assistance has expanded for teenage mothers and their children in the Villa Louise program.

Honorary degrees: Lebanon Valley College, Mt. St Mary's, Gettysburg College, Susquehanna University, Gannon University, Erie, Pennsylvania, 1993.

Archbishop emeritus of Baltimore, 12 July 2007.

He participated in the conclave of April 2005, which elected Pope Benedict XVI.

Created and proclaimed Cardinal by St. John Paul II in the consistory of 26 November 1994, of the Title of S. Maria degli Angeli (St. Mary of the Angels).