When Harlem’s identity shifted from village-outside-New-York, to suburb of New York in the late 1800’s, the ethnic makeup of its residents displayed striking patterns.
Looking at the map below you immediately notice the blue lines following avenues (more likely to have commercial space below with business owners or employees living above). These blue dots represent people who told the US Census that their birthplace was Germany. We don’t know if they were ethnically Jewish, Polish, or other minority groups living in the German lands, however.
Lastly it’s important to note that the buildings built along Avenues tended to be larger, and more likely to hold more people. We see this today walking around Harlem. While 3 story brownstones are typically found on streets. Brownstones on Avenues can reach 4 or even 5 stories tall.
There is some green scattered about (indicating a birthplace in England), but the pink dots (birthplace in Ireland) really stand out on the streets.
Zooming in a bit, you can see the pattern/s for 1880 birthplaces more clearly:
A great mural found on Park Avenue, just south of 116th Street.