25-year-old Amanda DiGirolomo of Phoenixville, Pa. and 25-year-old Bryan Botti of Baltimore, Md. were struck at Broad and Arch streets, near Philadelphia City Hall.
Action News is told both were in town for the Made In America festival.
It was just after 4:30 a.m. Monday when officers responded to the scene.
According to police, a Rosemont Taxi Cab Co. cab hit the two pedestrians, throwing them about 100 feet from the cab.
DiGirolomo was pronounced dead at the scene.
Botti died a short time later at the hospital.
A witness told police they estimated the taxi driver was going 50 miles per hour, 25 mph over the speed limit.
"The witness approximated the speed at over the speed limit," said Philadelphia Police Lieutenant Greg Brown of the Philadelphia Police Accident Investigations Division. "That hasn't been confirmed."
Police say the 41-year-old cab driver stopped and was taken to the hospital after experiencing chest pains. He is cooperating with police.
Investigators were awaiting toxicology results from blood work done at the hospital.
"The good thing here - he didn't leave the scene," said Brown. "He did the right thing and didn't make it an apparent crime by not leaving the scene. He stayed there."
Action News reached out to Rosemont Taxi Cab Co. The owners had no comment.
Amanda DiGirolomo was working part-time at the Phoenixville branch of the Freedom Valley Association YMCA.
In a statement to Action News Monday night, executive director Deirdre Wood said Amanda was "an amazing, vibrant young woman and will be terribly missed."
Wood said after graduating from Shippensburg University, DiGirolomo went to work for Vanguard while continuing to work at the YMCA part-time. Her mother and two sisters also worked at the YMCA.
"Amanda was a smart, outgoing and hardworking young woman," Wood added. "She had a bright future. Her thoughtfulness, caring smile and positive personality will be terribly missed. The loss of such a promising young adult brings great sadness to our 'Y' family."