As early as 1856, Missionary, Father Franz X. Weninger, S.J. ministered to the Catholic people in the New Ulm area. By 1858, the number of Catholics was large enough so that they began to talk about building a permanent church. A small wooden structure was begun at the north end of town on February 6, 1858. Despite their resolve, construction proceeded slowly. Before it was completed, the defenders of new Ulm destroyed it to prevent its use by the Dakota Indians as a barricade during the 1862 U.S. – Dakota conflict.
It was after this conflict that Michael Lauterbach transferred to Bishop Thomas L. Grace of St. Paul two lots in Block 111, Brown County for the site of the new church to be built. In April of that year, the first load of bricks was delivered on the site of the present middle school building of the New Ulm Area Catholic Schools. The cornerstone for the new church was laid on Sept 1, 1866.
In December 1868, Father Alexander Berghold was assigned the first Catholic pastor to New Ulm. He saw the completion of a 36x97 foot church topped with a steeple. Bishop Grace dedicated the new church on September 11, 1870.
Eleven years later, on July 15, 1881, a tornado destroyed the church. By September 1888, money had been raised for the present church building. The cornerstone was laid on May 4, 1890, the steeple was added in 1893 and the interior decorations were completed in 1903.
A German baroque influence can be seen in the interior decorations, done in heavy dark colors and gold leaf. The walls of the Cathedral contain numerous paintings of saints and religious scenes from the life of Jesus and the saints. In the sanctuary there is a painting of the Trinity and the 12 apostles. The original artist commissioned to decorate the church was Alexander Schwendinger who was assisted by Christ Heller and Anton Gag.
In 1940 a number of remodeling projects were undertaken. Two new entrances, one on each side to the church were constructed. A terrazzo floor was laid and the interior of the church was repainted with the original paintings being cleaned and restored.
On November 18, 1957, it was announced that the Church of the Holy Trinity in New Ulm was to be the new Cathedral for the diocese that had been created by Pope Pius XII in southern Minnesota. Bishop Alphonse Schladweiler was ordained the first bishop the New Ulm Diocese in this Cathedral on January 30, 1958. Bishop Raymond A. Lucker was installed as the second bishop in 1976 and on August 6, 2001, Bishop John D. Nienstedt was installed as the third bishop of the diocese. The Most Reverend John M. LeVoir was installed as the fourth and current bishop of the diocese.
The interior of the Cathedral was again renovated in 1987. A new north entrance with an elevator and handicapped restrooms was constructed. The lower level of the church was renovated as a community hall, named Leifeld Hall in honor of Monsignor Antony Leifeld, former pastor of Holy Trinity Cathedral.
