Well, Detroit was probably pronounced "day-TWAH" by its original French settlers.

Our current American pronunciation of Des Moines is a sort of compromise between true French and out-and-out Anglicanization. There are plenty of other French place names in the upper Midwest where the last Francophone left many years ago, at which time the pronunciation went up for grabs.

Back to New Orleans ~ I forgot one of my favorites, a wonderful example of mangled Greek:

Many residents of Socrates St. in Algiers say "SO-crates."

Anyone who has ever had the lightest exposure to philosophy knows how wrong that is!