As noted by many: The Cathedral-Basilica of St. Louis King of France is the oldest Catholic cathedral in continual use in the United States.
It was oddly bright inside for a cathedral and then I realized it’s all painted white and there are many clear glass windows surrounding the balcony.
See the statue of the horseman. It’s Andrew Jackson centered in its place in Jackson Square. The inscription reads “The Union Must And Shall Be Preserved”. Not what I expected to read!