It is the seat of the Roman Catholic Diocese of Boise and the chair of the Bishop of Boise, the church building was individually listed on the National Register of Historic Places in 1978, (lists maintained by the National Park Service of the United States Department of the Interior).

[3] That same year, the parish buildings were included as a contributing property in the surrounding neighborhood of the Fort Street Historic District.

[4] The first Roman Catholic Church parish / congregation in the territorial capital city of Boise was dedicated on Christmas Eve, December 24, 1870, but was destroyed in an unfortunate fire only 18 days later.

[5] Another replacement wood-frame structure was soon built that would serve the local Roman Catholic population of the faithful as the designated cathedral of the Vicariate Apostolic of Idaho, which was established and organized on the authority of the Church hierarchy in Rome, 13 years later on March 5, 1883, and its subsequent elevation a decade later as the current Roman Catholic Diocese of Boise and the ordination / consecration of the first Bishop of Boise, after it was established on August 25, 1893.

But soon a larger worship space / cathedral was needed and the Bishop of Boise Alphonse Glorieux purchased property in the city bounded by Fort, Hays, Eighth, and Ninth Streets.

Built in the Romanesque Revival style, the architects used the Cathedral of Mainz in western Germany and the Basilica of Saint-Sernin, Toulouse as their inspiration.

A rose window graces the front of the church and the center gable above the main entrance features a statue of St. John the Evangelist on its peak.

At the time, composer Frederick Fleming Beale, professor of music at the College of Idaho, was organist and choir director.

He wanted to restore all the stained glass windows that illustrate the stories of the saints, create more seating for the different groups of people who would come to the cathedral for ceremonies, celebrations, and worship, renew the canvas accents and designs in the interior, and bring in tasteful modern lighting fixtures which accented the classic renaissance look but accommodated to the needs of the citizens.

These details include the decorative gargoyles that metaphorically hold the weight of the church on their backs as a punishment for their sins, and the windows he restored.

St John's received an Orchid Award in 1981 from the Idaho Historic Preservation Council for outstanding work in restoration.