St. Aloysius Catholic Church is a historic Roman Catholic church in Carthagena, an unincorporated community in Marion Township, Mercer County, Ohio, United States. Built in the late nineteenth century, it remains the home of an active parish, and it has been designated a historic site because of its well-preserved architecture. Early parish history Local Catholics began to purchase large amounts of land in Cathagena from black people in 1856; the parish grew strong enough to establish a school and a cemetery in 1860, and St. Aloysius' Church was canonically erected in 1865. In their earliest years, the people worshipped in the chapel of the adjacent St. Charles Seminary. Throughout its history, the church has been significantly influenced by the seminary, which trained the priests of the Missionaries of the Precious Blood and provided pastors for the church. As its membership grew, the parish decided to construct a church building. Plans were laid and construction began in 1875; the cornerstone was laid in May 1877, and the church was consecrated on June 30, 1878; the parishioners had performed the construction work themselves. Under the pastorate of Gregory Jüssel, the church was greatly modified in the summer of 1905; only the tower and three of the walls remain from the original structure. Church building St. Aloysius Church is a Gothic Revival structure, five bays long and three bays wide, and officially one story high. Built of brick, laid in a stretcher bond, the walls rest on a foundation of stone rubble from Piqua, which includes a basement. A gabled roof of asphalt covers the rectangular church, which measures long and wide. One of the church's most prominent architectural elements is its tower: equipped with a white-painted wooden belfry and a tall spire, the tower rests on its own walls, thick. The entire building cost approximately $7,500 to erect; much of this amount was donated by other nearby parishes. Inside, the church's sanctuary includes elements such as white-painted altars and multiple sizes of pews: large pews for adults, and miniature pews for children. The interior is lit partially by many large stained glass windows; added more than 25 years after the church was completed, these windows were purchased by individual families within the parish. Few elements of the church are original from the 1870s. The middle of 1905 saw the completion of a wide range of alterations, including the removal of the original