The first Catholic church in the city of New Ulm, Holy Trinity, was started in 1857, but was demolished during the Dakota War of 1862.

[4] On November 18, 1957, Pope Pius XII founded the Diocese of New Ulm, taking its territory from the Archdiocese of Saint Paul.

[7] He also established a mission in Guatemala, assuming responsibility for staffing a parish in San Lucas Tolimán.

[9] He placed one of his parishes under interdict until every member received psychological counseling after a nun, trained in New Age spirituality, replaced a crucifix in the church sanctuary with a "cosmic pillow.

[13] Nienstedt's replacement in New Ulm was Reverend John M. LeVoir of Saint Paul and Minneapolis, named by Pope Benedict XVI in 2008.

[15] In 2017, the diocese filed for Chapter 11 Bankruptcy following numerous sexual abuse lawsuits against diocesan clergy.