The Motor City's oldest church building is Saints Peter and Paul at 629 Jefferson Street.
The cornerstone was laid in 1844 and it was consecrated as a cathedral in 1848--it is in the post-classical basilica style.
In 1877 Detroit's bishop deeded the church to the Jesuit Order so they could found a college--the school is now the University of Detroit Mercy. Adjacent to the church is the college's law school, most of the university is located on Detroit's northwest side.
The Jesuits wanted to close the church in 1971 and turn the historic structure into a law library for the college, but parishioners successfully sued to keep it as a house of worship.
That's the Michigan historical marker outside of the church.
UPDATE 9:10pm CST: There will be a mass mob at this church tomorrow morning.