The Philadelphia Stock Exchange was evacuated after smoke was reported on the trading floor late Tuesday morning.
Smoke was first sighted on the first floor of the exchange at 1900 Market Street in Center City just after 11 a.m., officials said.
The smoke was sucked into the building from a burning pile of leaves which caught fire outside, fire officials said.
Trading was halted and the building evacuated. The fire was extinguished at 11:37 a.m.
Exchange employees were allowed back into the building just before noon, though trading didn't resume until after 12:30 p.m.
The Philadelphia Stock Exchange is the nation's oldest exchange having been founded in 1790. It is now owned by NASDAQ.