1) The spindly structure of the steel holding up the wide, heavy roadbed deck.
2) Only four relatively small concrete posts holding up the bridge over the Mississippi River.
3) The obvious rust of the steel just over the concrete posts.
4) The large amount of exposed steel subject to effects of the wide temperature variations of Minneapolis weather (remember the city can get under 0° F. easily during the winter and can reach around 100° F. in the hottest summer days).
I'm surprised the bridge didn't collapse YEARS earlier.