Designed by Link and Haire, well known architects with offices in Butte and Billings, the church replaced the earlier Catholic Church, a small wood framed building from 1888. Begun in 1915, St. Leo's held its first mass on October 15, 1916 and was dedicated the next month on November 12.
Of red brick, the church was given copious amounts of stone trim, along with carved rafter ends and brackets under the generous cornices, heavy modillions to complement the brackets, several rose windows and copious brick corbelling. A large rose window graces the sanctuary over the main entrance, a matching one is to be seen on each end of the transepts, while four more smaller ones were placed high up on the tower.
The bell tower and steeple, incidentally, is 95 feet in height, with the belfry at the top, capped by a low hipped roof. Both above and below the belfry are heavy overhanging eaves with large modillions and carved rafter ends. Lines of terra cotta run around the tower above and below the arched belfry openings. Below the openings, on each of the tower's four sides, are three large stone plaques, a shield in the centre flanked by stone carvings of who we take to be Saint Leo.
The patron saint of the church, Saint Leo the Great, is depicted in a stained-glass window executed by Conrad Pickel Studios in 1953. Inside, the nave is 45 feet in height, taking the form of a half circle with a domed ceiling, and is capable of seating 440.
SAINT LEO'S CATHOLIC CHURCH
Lewistown’s first Catholic church was a small frame structure built in 1888. Visiting priests from distant St. Peter’s Mission, Great Falls, and Fort Benton celebrated mass for the French-Canadian, Indian, and settler congregations. The first resident pastor was appointed in 1893. Less than fifteen years later, Lewistown experienced the beginning of a population boom that extended to 1917. When the Catholic population reached a peak in 1915-16, the need for a new Catholic church became critical. The resident pastor, Reverend Victor J. Van den Broeck, and his building committee chose the well-known firm of Link and Haire to design the new church. Despite the architects’ concerns that the site was too swampy, work on the new church began in July 1915. Bishop Mathias Lenihan of Great Falls dedicated the new structure on November 12, 1916. The design of St. Leo’s Catholic Church incorporates a blend of Italian Early Christian and Romanesque styling on a Roman cross plan. The campanile, or bell tower, rises to a height of 95 feet. Blind arcading, exterior buttressing, rose windows, and intricate brickwork with terra cotta highlights complement the integrity and nobility of this magnificent building. During renovation of the interior in 1991-92, the original tabernacle was restored to use and the earliest confessionals were re-fashioned into the present altar.
From the NRHP plaque at the building