James Byrne was born on July 28, 1908, in St. Paul, Minnesota, to Philip Joseph and Mary Agnes (née McMonigal) Вyrne.

[5] He continued his studies at the Catholic University of Leuven in Belgium, where he earned a Doctor of Sacred Theology degree in 1937 with a thesis entitled: "Idea of Development of Doctrine in Anglican Writings of John Henry Newman.

[4] He received his episcopal consecration on the following July 2 from Archbishop Amleto Cicognani, with Bishops Thomas Welch and Francis Schenk serving as co-consecrators, at St. Paul Cathedral.

Archbishop Byrne also encouraged the growing cooperation among the Catholic and Protestant seminaries and colleges in Dubuque and often accepted invitations to participate in seminars and to speak to classes.

On one occasion, in an airport, he encountered a Protestant seminarian he had come to know through these activities who was going to interview for a parish position and offered his blessing for his success and for his future ministry.

Pope John Paul II accepted Byrne's resignation on August 23, 1983, and he was named Archbishop Emeritus of Dubuque.

He died while a resident at the Stonehill Care Center (operated by Franciscan Sisters) in Dubuque on August 2, 1996, and was buried in the mortuary chapel of St. Raphael's Cathedral along with other deceased bishops and archbishops of the archdiocese.

Byrne faced significant controversy regarding his handling of clergy sexual abuse cases during his tenure as Archbishop of Dubuque.

[7] When allegations of abuse emerged, Byrne's typical response was to remove priests from their positions and send them for what was considered appropriate care or treatment at the time.

He showed particular faith in psychological and mental health treatment approaches, combined with traditional spiritual interventions such as retreats, prayer, and penance.

His administrative decisions were reportedly influenced by the mental health expertise available at the time, though these practices would later be recognized as inadequate for addressing clergy sexual abuse.