Essex County, NJ is pretty polarized. The high median income is from some of the suburbs that have little in common with Newark and Irvington.
This is true, but incomplete.
Most of the black areas in Essex County are poor and urban (Newark, Irvington, Orange), and most of the high-income areas are heavily white (Millburn, Livingston, the Caldwells, etc.).
However, in between those two extremes are a few towns which are high-income but
also have substantial black populations: Maplewood, South Orange, Montclair, West Orange. Those four towns have a sizable number of affluent blacks, though I think all of them are white-majority.
And there's even a corner of the county which is neither particularly black nor particularly high-income: the Bloomfield/Belleville/Nutley trio, which is historically heavy Italian/Irish, and is home to a growing number of Hispanics. Eh, I guess Nutley is somewhat affluent.
