I observed this in New England while living in a city with evenly distributed population. The polling locations were more abundant in the wealthier side of the city. This may not have been straight racism; there was no way for me to determine why this was the case. Looking at a map of median income and polling locations made it pretty obvious to me at least that polling location choice was biased.
It could be as simple as "wealthy areas get more county services." There are practical considerations when choosing polling places, like the availability of parking and enough space to accommodate a line, check-in tables, voting booths, and ideally separate entrance and exit doors. Public schools and county rec centers are go-to locations because the county (who administers the election) already owns them and they have the space needed. Churches are great too, but they require having an agreement with a private organization.
By New England I guess you just mean Boston and the Boston area right? I'm unaware of any other huge concentrations of African Americans in that region. Boston is well known for its racism, I actually had a friend from Boston when I was living in Vicksburg MS and they got along there much better than me.
