the classic philly/b-more accent is almost exclusively a white phenomenon...
or, I mean, white & black people from those towns tend to have different, equally distinctive accents. with a good deal of overlap, depending on what part of town you're from - i.e., in Philly, West Philly (black, outside the campuses vs. deep South Philly (Italian) vs. Kensington (mishmash of everything). I'm not as familiar w/Baltimore but say, East Baltimore vs. Southeast (which, if I recall, is heavily "ethnic white"; Slavs, Greeks, Italians, etc.).
the "white" Baltimore accent is a weird one tho. they say "warsh" instead of "wash" & "wooter" for "water". "to be" is often left out of phrases, e.g. instead of "my hair needs to be cut" it's "my hair needs cut". having lived in both Philly & Pittsburgh & spent a fair bit of time in Bmore I've always thought the accent was closer to PGH than to Philly. both working class towns with a lot of white people. so is Philly I guess but not in quite the same way.
the PGH accent (mostly talking white people again) is, if anything, even stranger. the biggest thing is "yinz" - people from PGH are Yinzers - it corresponds to "you guys", like "y'all" or vosotros
in Spanish. also - this would always me laugh when I heard it - rubber bands are "gum bands". beanies are "toboggans". I used to date a girl from rural SW Pennsylvania & her accent was even thicker, Appalachian, "creek" become "crik" & so on.
really there's all kinds of bizarre regional accents in the U.S. New England's (especially north of Boston), the no-holds-barred Spanglish of the southwest, the holdover Scandanavianisms of Wisconsin & Minnesota, etc etc it's kind of cool actually. I guess this is true for England also - Brummie, Geordie, Manc, etc