George Carlin grew up on West 121 Street in Manhattan during the Forties and early Fifties, with Columbia University to the south and Harlem to the north. He described his neighborhood as a polyglot place where he learned to hang out with different kinds of kids. Out of that experience, I suspect, came his penchant for crossing boundaries and making wisecracks that eventually got him kicked out of Cardinal Hayes High School. But not everyone lived that way in northern Manhattan in those days.
Blocks and streets had a strong racial or ethnic charater. The most interesting of them were home to a mix of people. But too often, on either side of the mixed blocks, were streets defined by the majority that lived there--white, Black or Hispanic.
By the Fifties, the Black and Puerto Rican population in northern Manhattan was growing. The Irish, who tended to live in walking distance of Roman Catholic parish churches, were either leaving for the suburbs or moving north to parts of Washington Heights or Inwood with distinctly Irish communities.
There was a nasty edge to all of this that came out in gang fights over turf. But out of this tumult also came blocks where Black, Hispanic and Irish guys played ball together and learned to get along. Guys who thrived in this sort of situation--like an Irishman I know who played football for pub teams, went out with a Puerto Rican girl, and dug Mongo Santamaria--weren't necessary the norm. But they were special--just like George Carlin.