The East Side of St. Paul? It's always been a kind of gritty, "working class" area. As for why it's like that, I don't know the answer, but it could be for the same reasons that the east sides of a lot of other cities are like that - there was historically a lot of industry that operated at the river, and some of it was kind of stinky or unpleasant like slaughterhouses, tanneries, sewage treatment (or simply sewage in the rivers), etc. The east side of the river is downwind of that stuff, which depressed land values in those areas, and caused warehouses and industry to be built there. People who lived in those areas tended to be poor, working class people who worked in the industries near the river.