For example, in Jacksonville, Fl. where my daughter used to live, there is a neighborhood on the West side of the river. It was at one time a good neighborhood but as suburbs opened up...people wanted newer homes and they moved out. Property valued fell and so forth.
A Historic neighborhood was declared by the city or county. And now after about 10 years the poorer people of all groups has been having to move as absentee landlords sell the homes to young professionals who renovate them and move in. The entire area is still in flux and is NOT completely gentrified....but it was looking pretty good the last time I saw it not too long ago.
It is apparently been fairly successful for improving the area, but the poor people of all colors must keep right on moving out...into other low rent areas...and so it goes....