St. Charles Seminary and Chapel - Carthagena, Ohio

 St. Charles Seminary and Chapel are located outside of Carthagena, Ohio. The current seminary building was constructed over a six-year period and finished in 1922. The seminary was designed in the Late Gothic Revial architectural style by Herman Gaul, an architect out of  Chicago. The Romanesque Architectural Style chapel was designed by Anton DeCurtins & Bros. and built in 1906. The seminary was built around the chapel. The seminary closed in 1969 as a consequence of declining enrollment. In order to accommodate the retiring priests and Religious Brothers of the congregation, the former seminary was converted into the St. Charles Center, a retirement home for them. As this need peaked in 1980s and 1990s, the center became converted into a senior living center for lay people as well. The St. Charles Seminary is historically significant because it was the training center for the Fathers of Society for the Most Precious Blood from 1860 until 1968. The brothers still maintain the buildings and farm; approximately 940 acres in Marion and Granville Townships in Mercer County. Posted to the National Register of Historic Places on January 26, 1979. GPS: 40.43267°N, -84.56371°W.

St. Aloysius Catholic Church - Carthagena, Ohio

 St. Aloysius Catholic Church is a historic Roman Catholic church in Carthagena, Ohio. 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. Back in the 1800s, 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. The modification included the addition of a sacristy, the placement of the present stained glass windows, and the expansion of the sanctuary. The architect was Anton DeCurtins, who designed the church in the Gothic Revival architectural style. Posted to the National Register of Historic Places on July 26, 1979. GPS: 40.43653°N, -84.57007°W.

St. Rose Catholic Church Complex - St. Rose, Ohio

St. Rose Catholic Church Complex in St. Rose, Ohio. Complex includes church, rectory, and one room schoolhouse. The church was built in 1912 in a High Gothic Revival Style, designed by DeCurtins, a Swiss immigrant who lived in Carthagena, Ohio. Located adjacent to the church on the west is a three-story rectory. Built in 1905 at a cost of $6,000. Located adjacent to the church on the east is the single-story St. Rose schoolhouse, former parish school, built in 1892. Built as a one-room school, the building was modified in 1941 and converted into a two-room school. It operated until closure in 1957. After its closure, the old school was modified to be a parish hall and a recreation center. Posted to the National Register of Historic Places on July 26, 1979. GPS: 40.40742°N, -84.51506°W.

Calvin E. Riley House - Celina, Ohio

Calvin E. Riley House in Celina, Ohio. Calvin Erastus was born in 1830 and came to the Celina area as an adult when he engaged in farming and milling. He became a partner in a private banking business which was incorporated in 1893, and later merged into the Commercial Bank Company of Celina. In 1896, Calvin had this elaborate Queen Anne architectural style house built. Following Calvin into the leadership of the Commercial Bank was his son Ashley, grandson Roscoe, and great-grandson David K. Riley. Calvin passed away 1914. James Zura Riley, another son of Calvin's, daughter Lena, who died in 1974, was the last Riley to live in the house. The house has mostly remained unchanged since it was built. Posted to the National Register of Historic Places on November 30, 1978. GPS: 40.54881N, -84.56951W.