And officials now say a nearby cemetery is in danger of being undermined.
The sinkhole began to open up at 8:45 a.m. Thursday after a water main burst beneath the 300 block of North 10th Street.
Crews arrived on the scene to find and repair the broken main, even as the sinkhole continued to grow.
Most of the residents learned of the danger when firefighters came banging on their doors.
"He said, 'You have time, get some things together and you're going to have to leave.' So packed up my daughter and the cat we got out of the house," said resident Karen Martz of Allentown.
Dwayne Glover discovered the water main break. He went to his basement to find out why they had no water pressure.
"As I'm searching to find out where the water's coming from, I fell through the concrete floor," said Glover.
After he crawled out, Glover could see a river of water rushing bye under the concrete. He called the water department and then tried to leave the house with his family.
"I tried to open the door to walk the dog and I couldn't open the door. I couldn't get out of my house," he said.
The house had shifted and Glover had to force the door open. The water department had to dig up the street to cap off the broken main.
In the meantime, a large sinkhole opened up revealing another hidden danger.
A 12-inch natural gas transmission line had been undermined. There's no shutoff nearby, and a break would have cut off gas service to most of the city and Whitehall Township. The gas company used webbing to stabilize the main.
The evacuated residents were left wondering if they'd ever be able to go home again.
"That's my house with everything in there. I just need to know when I can at least get in and get something, get some clothes for my kids, get the necessities that are in there and get out," said Yahaira Delgado
Five homes are damaged. Three of them will probably have to be demolished.
"There are foundation cracks. There's water damage in the basements. There's also some shifting of the houses that we saw," said Allentown Assistant Fire Chief Lee Laubach.
The situation has been stabilized for now, but there is one other complication. The ground under part of the cemetery across the street has also been undermined. The city has obtained a court order to exhume some of the bodies before making repairs.
In all, 13 homes have been evacuated with a total of 25 residents displaced. A local school is being used to shelter the displaced residents.