Charles Street, between Read and Madison. Never on Sunday sells the most Philly-like Philly cheesesteaks in Baltimore. The menu covers almost any combination of toppings one can come up with, and the steaks are served up hot, greasy, and messy as can be. The servers are loud and the seating appears perilous. The restaurant (if you'd go so far to call it that) sits in Baltimore's Mount Vernon, about eight blocks from the Inner Harbor.
It's the only appropriate place to go in Baltimore for an amazing cheesesteak.