And I'll add, many of the neighborhoods are geographically defined by rivers, streams, hills, mountains, hollows, bridges, railroad tracks. The topography more than anything dictated the design (or lack of) for the Burgh and Allegheny County.
Thank you. I meant to add that, but hit 'post' too soon. Many neighborhoods are small with natural boundaries that makes casual mixing difficult. If your weren't from the neighborhood, you were automatically suspect even if you were just over the next hill.