When French explorer Jean Nicolet entered the Green Bay areas in 1634, he was followed by Jesuit missionaries.

[6] In 1669, Reverend Jacques Marquette arrived at the mission after Allouez moved to the Fox River Valley.

Allouez celebrated Mass with a Native American tribe near present-day Oconto, Wisconsin in December 1669, the feast of St. Francis Xavier.

The mission moved to Red Banks for a short time in 1671, and then to De Pere, where it remained until 1687, when it was burned.

The missionaries worked with the Fox, Sauk, and Winnebago tribes, protected by Fort Francis near Green Bay.

[5] When the British took control of New France in 1763 after the French and Indian Wars, the bishops in Quebec continued to have jurisdiction in the region.

In 1837, the missionary Reverend Florimund J. Bonduel traveled from Green Bay to visit the French fur trader Solomon Juneau in Milwaukee.

Kelly celebrated mass in the Milwaukee courthouse until 1839, when he opened St. Peter's, the first Catholic church in the city.

In 1871, the Dominican Sisters of Sinsinawa established the Saint Regina Academy for girls and boys in Madison.

[12] Saint Paul's Catholic Student Center, serving the University of Wisconsin Madison community, was founded in 1906.

[16] In his first year as bishop, O'Connor established the Blessed Martin Guild to promote racial understanding and convert more minorities to Catholicism.

[21] After O'Donnell retired in 1992, Pope John Paul II named Bishop William Bullock of the Diocese of Des Moines to replace him.

[24] Morlino supported the application of Summorum Pontificum, an apostolic letter issued by Pope Benedict XVI in 2007 on the use of the Tridentine Mass.

[26] In May 2009, Morlino announced that due to budget cuts, he was closing the Catholic Multicultural Center, which provided food and other support for residents on Madison's south side.

[28] In March 2009, Morlino dismissed Ruth Kolpack from her post as a pastoral associate at St. Thomas the Apostle in Beloit, citing her breaches of orthodoxy.

Morlino also demanded that she renounce her 2003 doctoral thesis, which advocated women's ordination in the Catholic Church and the use of inclusive language relating to God.

William J. Connell was arrested and charged with arson and other crimes, but was deemed incompetent to stand trial due to paranoid schizophrenia.

[32] In September 2003, at a legislative hearing in Madison, a woman from Sun Prairie accused Reverend Gerald Vosen, pastor of St. Joseph's Catholic Church in Baraboo, of sexually assaulting her brother when he was age 14 in the 1970s.

An Eau Claire man sued the diocese in February 1994, claiming that he had been sexually assaulted by Reverend Michael Trainor in the summer of 1982.

[37] The plaintiffs claimed that Bishop O'Donnell was aware of Trainor's abuse of children and transferred him from one parish to another without reporting him to the police or parishioners.

[41] In March 2020, Bishop Hying announced that investigators had found two sexual abuse allegations against Reverend Patrick Doherty, a retired priest, to be credible.