The only results I can find are from weather related sites which all state “The Mississippi River froze at New Orleans”.
I can accept that maybe some backwater areas may have iced over near shore, but for a river-wide freeze I’m highly skeptical.
Even here in southern Michigan its pretty rare to see a river freeze over solid in an average winter. Mostly they tend to freeze along the edges and around objects sticking up.
I know it can get mighty cold down that way but I suspect it takes some extended cold even to get a thin skim of ice in the backwaters. After all the water cools much slower than the air.