According to Lance Hilldebrand who keeps track of these things, the number of mattresses and ladders which fell onto St. Louis roadways in 2017 came to:
Mattresses 163 1/2
I'd guess these numbers could well be higher since some don't get reported. This compares to 2016 which saw:
It's getting worse out there, so be aware. That half a mattress which fell in October along 170 still makes me laugh.