In 1867, the first resident pastor came to serve the Catholic community in the parish church, which was built five years previously in Sioux City. Until that time, Sioux City was a mission territory.

The Cathedral of the Epiphany was begun in 1891, as St. Mary’s Church. With Father Timothy Treacy as the pastor at that time.

On April 5, 1892 , Bishop Hennessy ordained Thomas McCarty to the priesthood. Father McCarty was a member of St. Mary’s Parish and the first young man from Sioux City to become a priest. Several days after his ordination, Father McCarty came to Sioux City and offered his first Mass in the large hall of St. Mary’s School. St. Mary’s School, which was constructed in 1889, at a cost of $30,000, was located on the Southeast corner of 10th and Grandview Street.

A new church building was planned and was intended to serve the pastoral needs of a growing number of Catholics who lived in the central part of Sioux City . The parish was made up of an ethnically diverse group of immigrant parishioners, with Irish and Germans being the predominant group. In 1892, a nationwide economic depression threatened the local economy, and completion of the building project was postponed.

For a period of nearly 10 years, the members of St. Mary’s Parish worshipped in the basement of the present church building. Once the Diocese of Sioux City was established in 1902, it was decided that St. Mary’s Church would serve as the Cathedral. The church was incomplete at that time, and it was recommended that the upper church be completed. On Sept. 8, 1904, the building was named the Cathedral of the Epiphany.

Over the past 100 years, the Cathedral of the Epiphany has been redecorated on a number of occasions. The photographic records of these various renovations exhibit a wide array of design motifs. However, the general arrangements of furnishings in the interior remained the same until a major renovation was undertaken by Bishop Joseph Mueller in 1961.

When the building was first constructed, the towers were not completed. Bishop Mueller completed the eastern façade with the addition of two spires that still form a prominent part of the Sioux City skyline.

The most recent changes are the restoration project that started in the summer of 1994. The roof and gutters were replaced, as well as the exterior tuckpointed. Several other exterior changes were made such as the removal of the worn bridge between the church and rectory, which was replaced with a courtyard. The interior has been restored to keep it as close as possible to the original and in keeping with the architecture.

In the months during the renovation of the Cathedral, the church of St.Thomas at Emmetsburg permanently closed. The people of St. Thomas Parish donated their altar and stations of the cross to the Cathedral, due to the similarity of previous items that were once in the Cathedral.

In 1987, the priceless stained glass windows, a product of the Mayer Co. Studios in Munich , Germany , underwent a complete restoration.

The toll of the years was increasingly evident on the old Cathedral School . As early as the 1940s, the people of the parish were beginning to talk about replacing the old landmark. The last class to graduate from Cathedral High School graduated in June 1, 1949 . The new Catholic high school of Sioux City was opened in 1949, Bishop Heelan High School . With the Sisters of Charity, B.V.M., continuing to teach at Heelan.

By 1957, the need for a new education facility was evident at Cathedral and at Heelan High School. A fund drive was held and with its success, three lots were purchased on the corner of 10th and Douglas St. The total cost was $40,500. The new grade school was built on the site and opened in September of 1959.

The old school site was consolidated in 2001 with St. Joseph and St. Boniface, with an enrollment of approximately 300 students. It now houses the Cathedral offices and is used for religious education.

Cathedral Parish has fostered many vocations during their lengthy and illustrious history. In addition, Cathedral Parish has continued to grow and expand its diversity. They have also welcomed Hispanic and Vietnamese brothers and sisters into the parish over the years. Masses are currently offered in English, Spanish, Vietnamese, and Latin.