East Side
A very interesting hypothesis on why the east side of cities are often poorer (which I can’t say I’d notice, but I’ll take their word for it):
The reason for this is that in much of the northern hemisphere, the prevailing winds are westerlies – blowing from west to east. The massive, unchecked pollution from these early industries would therefore drift eastward, making the air quality much lower in the east end of cities, lowering the desirability (and price) of the housing. Middle classes preferred the cleaner west ends.