In 1817, when the Italian–born Father Joseph Rosati arrived in St. Louis, he found a ramshackle church, a windowless log cabin for a rectory, and 2,500 people disinterested in religion of any sort. On the best of days, that would fail to cheer a missionary’s heart.

But this wasn’t just any day. Rosati had come to St. Louis to prepare the church for the arrival of the Most Reverend Louis William DuBourg, the newly ordained bishop of Louisiana and the Two Floridas, who was coming to set up his episcopal see in St. Louis.