St. John's Cathedral was designed by one of the first architectural firms to work in Boise, Tourtellotte & Hummel.
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.
The exterior is Boise Sandstone, quarried just above the city at Table Rock.
The building is cruciform in shape and measures 170 feet (52 m) from front to back, 95 feet (29 m) at the transepts and 65 feet (20 m) in the nave.

The building was designed to have two towers topped with spires flanking the main façade, but they have not been completed.
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.
Corbeling, a continuous band of small projecting arches, encircles the building at the roofline.
A fléche rises above the crossing.

The stained glass windows in the nave depict scenes from the life of Christ.
The large window in the north transept depicts the Adoration of the Magi, flanked by windows portraying St. Alphonsus Ligouri and St. Theresa of Avila.
The south transept window depicts the Ascension and is flanked by windows portraying St. Patrick and St. Rita.
The windows in the sanctuary depict St. Joseph on the north and the Blessed Virgin Mary on the south.
In the apse are windows portraying the Sacred Heart of Jesus and the Immaculate Heart of Mary.
They are flanked by windows portraying the Four Evangelists.
Although some of the art glass was installed by the Intermountain Glass Company of Boise, the stained glass windows were designed and installed by the John J. Kinsella Company of Chicago in 1920, except the window portraying the Holy Spirit in the center of the apse, which was installed in 1979.
St. Cecilia is depicted in the window above the pipe organ.

The 3-manual, 2900-pipe organ was installed by Tellers-Kent in 1921.
At the time, composer Frederick Fleming Beale, professor of music at the College of Idaho, was organist and choir director.
St. John's Cathedral was designed by one of the first architectural firms to work in Boise, Tourtellotte & Hummel. 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. The exterior is Boise Sandstone, quarried just above the city at Table Rock. The building is cruciform in shape and measures 170 feet (52 m) from front to back, 95 feet (29 m) at the transepts and 65 feet (20 m) in the nave.
The building was designed to have two towers topped with spires flanking the main façade, but they have not been completed. 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. Corbeling, a continuous band of small projecting arches, encircles the building at the roofline. A fléche rises above the crossing.
The stained glass windows in the nave depict scenes from the life of Christ. The large window in the north transept depicts the Adoration of the Magi, flanked by windows portraying St. Alphonsus Ligouri and St. Theresa of Avila. The south transept window depicts the Ascension and is flanked by windows portraying St. Patrick and St. Rita. The windows in the sanctuary depict St. Joseph on the north and the Blessed Virgin Mary on the south. In the apse are windows portraying the Sacred Heart of Jesus and the Immaculate Heart of Mary. They are flanked by windows portraying the Four Evangelists. Although some of the art glass was installed by the Intermountain Glass Company of Boise, the stained glass windows were designed and installed by the John J. Kinsella Company of Chicago in 1920, except the window portraying the Holy Spirit in the center of the apse, which was installed in 1979. St. Cecilia is depicted in the window above the pipe organ.
The 3-manual, 2900-pipe organ was installed by Tellers-Kent in 1921. At the time, composer Frederick Fleming Beale, professor of music at the College of Idaho, was organist and choir director.
Cathedral of St. John the Evangelist (Boise, Idaho)