Father Mazzuchelli, pioneer missionary and skilled architect-builder, designed more than twenty churches in mining towns in the Upper Mississippi region in the 1830s and 1840s. St. Augustine is the only one that survives unaltered. Italian-born Mazzuchelli ministered to settlements in the Fox River Valley for five years before he became in 1835 the first Catholic priest in southwestern Wisconsin’s lead-mining region. He also served as a missionary to the Ojibwes, Menominees, and Ho-Chunks, established several Catholic schools, and founded the Dominican Sisters of Sinsinawa, Wisconsin’s first religious order of women.
For the New Diggings church, Mazzuchelli began with a basic Greek Revival design, but added Gothic elements. The front-gabled roof and cornice returns suggest a classical pediment; a wooden frieze, embellished with frets and dentils, wraps underneath the eaves; wooden Doric pilasters define the building’s corners; and squared Doric columns and a meandering frieze grace the rooftop bell tower. Gothic details include lancet grooves in the pilasters and columns, pointed corbeling, a pointed-arched entrance with simple tracery in its transom, and pointed-arched windows on the church’s sides. Unusual is the choice of materials. Mazzuchelli used nine-inch-wide wooden planks for the exterior walls, grooving them to mimic stone blocks. Inside the church, the crude pews and the finely carved altar railing are original. The Knights of Columbus use the church for an annual mass.