[3] In the late 1840s, Father Salzmann of St. Mary's Church began organizing those German-speaking Catholics of the south side into Holy Trinity parish.

[1] German-born architect Victor Schulte designed the main block of Holy Trinity (as he had St. Mary's) rectangular with brick walls which have weathered to a warm gray.

The church was dedicated by John Henni, the first Archbishop of the Roman Catholic Archdiocese of Milwaukee, on September 22, 1850.

[4] The steeple was added in 1862, designed by German-trained Leonard A. Schmidtner, consisting of an octagonal tower rising behind the front entrance of the church, leading to a smaller octagon at the next stage, leading to a tall spire with four windows, topped with a cross high above.

[4] Over the years the Germans have waned in the surrounding neighborhood, and Puerto Ricans and Mexican-Americans have increased.