As the village of Delphos grew with the Miami and Erie Canal, the parish's prosperity likewise increased;[2] like St. Michael's Catholic Church in Shelby County to the south,[4] the church's architecture demonstrates the wealth that came from the commerce along the canal.

Leading features of the church's interior include a prominent rib vault, two rows of columns in the nave that are topped with Corinthian capitals, and an altar built to resemble that of Rome's Basilica di San Clemente.

It fills an entire city block, and its tower is by far the most prominent part of the community's skyline; accordingly, it has been likened to a cathedral.

[2] In 1980, St. John's Church was listed on the National Register of Historic Places because of its architectural significance.

It is the only church on the National Register in Allen County, and one of three buildings in Delphos so to be recognized.