It's a Polygonum or Persicaria. The top leaf looks a bit narrow so I'm not sure which species. If you could post a picture of more of the plant showing the lower leaves we may be able to be more precise.
I like in Chicago too, I see these everywhere . I think it's Polygonum persicaria, or Persicaria macula. I know it's in this knotweed type of family, however the ones i see often do not have the spot on the leaves.
It's a Polygonum or Persicaria. The top leaf looks a bit narrow so I'm not sure which species. If you could post a picture of more of the plant showing the lower leaves we may be able to be more precise.
