I live in South Philly and I never use the term "art museum area". It makes me cringe when i hear it.

When i say "Fairmount" i'm referring to everything on either side of Fairmount Ave. Everything between 17th & the Parkway and Girard and Spring Garden.

Everything between Spring Garden and the Parkway and out to 17th is what i call "the Parkway." Again this is just what it means to me as an outsider.

But those names definitely don't extend to the other side of Broad St.

No Libs is Delaware to 7th and Spring Garden to Girard. Old City is the same thing but between Spring Garden and Walnut. You can visit the civic association websites for that information.

Broad St. to 11th between Vine and Spring Garden is the Loft District.

I think a general rule for anyone in the real estate or planning professions should be to defer to local civic associations first. When there's a no-mans-land between associations (like the two block gap between Pennsport and Passyunk Square) i would tack it on to the closest one.