On July 24, 1900, Pope Leo XIII erected the new Diocese of Sioux City by separating 24 counties in northwestern Iowa from the Archdiocese of Dubuque.

[1] The pope appointed Philip Garrigan, vice rector of the Catholic University of American in Washington, D.C., as the first bishop of the new diocese.

In 1929, Heelan donated land in Sioux City to the Sisters of St. Francis for the establishment of Briar Cliff College for women.

[4] In 1947, Pope Pius XII named Reverend Joseph Mueller of the Diocese of Belleville as coadjutor bishop to assist Heelan.

[5] In 1997, John Paul II named Reverend Daniel DiNardo from the Diocese of Pittsburgh as coadjutor bishop to assist Soens.

[3] To replaced DiNardo in Sioux City, Benedict XVI appointed R. Walker Nickless of the Archdiocese of Denver as the seventh bishop of the diocese.

In 2016, the diocese announced plans to consolidate 41 parishes due a shortage of priests and decreased mass attendance.

[8] In 1992, after receiving multiple sexual abuse allegations, the Diocese of Sioux City forced Reverend George McFadden to undergo treatment and retire from his pastoral position.

[12][13] In November 2008, the diocesan review board for the diocese reported that there were several credible accusations that Soens had sexually abused minors.

[14] In October 2018, the diocese admitted that for several decades it had concealed sexual abuse committed by Reverend Jerome Coyle.

Coyle confessed his criminal history to Soens in 1986, who placed him on a six-month medical leave, but did not report the admission to police or suspend him.

[15] In October 2019, Samuel Heinrichs sued the diocese, claiming that he had been physically and sexually abused when he was ten years old by Reverend Dale Koster.