Beginning with Owen Gallagher in 1860, Catholics began to migrate into Celina,[2]: 233  and starting in 1864, Mass was celebrated biweekly in a factory owned by one of the members.

At this time, no priest lived in Celina; the celebrant was typically Joseph Gregory Dwenger, then the pastor of Holy Rosary parish in nearby St.

[3] In the early twentieth century, it was widely considered the finest church building in all of northwestern Ohio,[2]: 234  and decades later, its architecture still dominates all of downtown Celina.

The first priest to live in Celina was Theopistus Wittmer, who arrived in 1876; the members acquired a small frame house to use as a rectory.

[7] The church itself is a large brick building constructed in the shape of a Greek cross; it was designed by Andrew DeCurtins of Lima and built under the supervision of John Burkhart of Kenton.

Worshippers may enter the building through its eastern end; the facade is pierced by three large doorways and a massive rose window.

[9]: 2–3 Located immediately west of the church, the Immaculate Conception rectory is a large square three-story brick house.

The house is built in a combination of styles; it includes many Italianate details, but its design appears to have been influenced by the architecture of the Sears Modern Homes.

[6] Due to falling enrollment and increasing expenses, the school was losing significant amounts of money by the late 2000s.

[5] Located on the eastern side of Walnut Street across from the other buildings of the church complex, the former Immaculate Conception High School was built in 1933 under the supervision of William and Joseph Forsthoff.

[9]: 3  Although Fred DeCurtins designed the church building constructed in 1937 for the new parish in the northern Mercer County village of Rockford,[9]: 4  architectural historians believe that Immaculate Conception High School was the last building designed by the DeCurtins family for an entity connected to the Missionaries of the Precious Blood.

[11] Three stories tall, the high school is a brick and stone building constructed on a concrete foundation with a basement and topped with a flat composite roof.

At the same time, the same designation was given to more than thirty other churches and other buildings in far western Ohio that were related to the Missionaries of the Precious Blood, using the multiple property submission process.