The fire broke out around 4:15 a.m. on the 1200 block of Spruce Street.
One firefighter suffered a minor injury and was taken to the hospital for treatment.
"I had heard the sirens. They got a little too close, so I came downstairs, looked out, saw flames coming out of the second floor," said Tim Mosca.
Engine 1, one of the fire companies restored last year, arrived to heavy flames and smoke.
Residents in neighboring buildings woke up and evacuated.
"I could already smell the smoke in my apartment. I'm on the second floor. I think it was a third floor fire on the other building," said Kim Greenfield."I came to the front, looked out the window, looked to my right, and saw that there were flames, grabbed my cat, and now here I am."
Philadelphia Fire Commissioner Adam Thiel explained some of the flames were difficult to access due to the age and configuration of the building.
"We did have to actually evacuate our firefighters from this incident due to some interior structural compromises so this has been what we call an exterior attack," Thiel said.
Thiel added the fire had damaged surrounding buildings.
The Red Cross responded to assist around 20 people who were displaced.
The cause remains under investigation.