It was declared under control at 10:29 a.m., but firefighters continued to pour water on the building as dark smoke soared skyward.
Scott Tennesen, president of the Latin Cruiser Car Club, said the group housed 15 classic cars in the building.
The cause of the fire is under investigation.
Robert Wright, the building's owner, said there was rumor that a car owner doing bodywork in violation of garage policy may have sparked the fire.
Tennesen said the classic vehicles stored in the garage included two 1971 Ford Mavericks, a 1966 Ford Mustang Shelby GT 350, a 1949 Ford, a 1976 AMC Pacer, a 1978 Ford Pinto wagon, a 1961 Cadillac, a 1961 Ford Falcon, and a 1956 Chevrolet panel truck.
Most of the cars were insured, he said, but probably are irreplaceable.
"You can try to find one that's similar, but you can never replace the time, money, and effort spent on those cars," Tennesen said.
Alvin Taveras, who lives near the garage and rents two berths for his cars, said he thought his 1993 Honda Civic hatchback was destroyed. He said he had recently spent about $2,000 preparing the car to race at a New Jersey track and had no insurance for it.
"I was always afraid of this," said Jose Rodriguez, another neighborhood resident who kept his BMW in the garage and had also done work on his car. "My hard work is going down the drain."
The Latin Cruisers Car Club participates in shows throughout the region and hosts weekly cruise nights at a Chick-Fil-A in Port Richmond, where neighborhood residents can see the club's cars on display.
Contact staff writer Julie Zauzmer at 215-854-2771 or email@example.com.