Holy Trinity Church is influenced by German Zopfstil, a variation of classical design. It was popular in Germany in the 1840s, just as the first wave of German immigrants arrived in Milwaukee. When Milwaukee’s South Side neighborhoods attracted a Hispanic population after 1960, the church changed its name to include Our Lady of Guadalupe, reflecting its growing membership. The Catholic immigrants from southern Germany and Austria who settled in Walker’s Point asked German-born Schulte to design their parish church; its octagonal tower, designed by German-trained architect Schmidtner, was completed in 1862. The restrained Zopfstil influences include round-arched windows, a large tower centered on the front of the building, a low-pitched roof, and plain brick pilasters, which define each bay. Brickwork accents include round-arched corbeling around the building and, on the main elevation, a paneled balus-trade and blind, round-arched windows. The church interior retains its mid-nineteenth-century decoration. Minimal alterations include the installation of the pipe organ in 1878 and the addition of three richly carved wooden altarpieces in 1890.
The church complex has a three-story Italianate parish grade school (1867; 621 S. 4th Street), a Romanesque Revival brick convent (1888; 423 W. Bruce Street), and a large Queen Anne brick rectory (1892; 613 S. 4th).