I was going to make a similar point that Balto shares much in common with Philly. The architecture and history follow very similar paths. I would take train as the authority, but rowhouses in parts of Queens and Brooklyn remind me of their counterparts in Balto and Philly. In my visits I find more similarities than differences.
As to the demographics, Balto was a significant some to white ethnic immigration and was the second largest port of entry after NYC. Residents of Irish ancestry make up 13% of the population in Balto. Little Italy is an important neighborhood and was the childhood home of Nancy Pelosi, the daughter of Baltimore Mayor D'Alesandro. Before the Civil War the black population of Balto was predominantly free, though there were some slaves, and today makes up the largest ethnic group as it does in Philly.
What I'm thinking of more than anything is the two-story lower-class housing like this:
(in Philly)
http://upload.wikimedia.org/wikipedia/commons/1/19/Douglass_Houses_Baltimore.JPG (link 'cause the picture is huge)
...which is often found on on really tiny side streets that are much closer together than you find in NYC. Most of Brooklyn's row home stock is three stories at least, often four; where you have two story row housing in NYC it's almost always further from the core, and has setbacks and front lawns, like so:
Note that you do get this style in Philly, too: but, again, further out from the core. And NYC of course has a much larger prevalence of multi-story apartment buildings. And, of course, in Boston you get
triple-deckers instead. (I was struck by the prevalence of detached three-story buildings with balconies on every floor
long before I knew what it actually was. It's a really distinctive feature of New England housing.)
I agree, also, that Baltimore does have a history of "ethnic" immigration and the lack of such is overstated.