"Operation Santa" offers letters to the public from low income families.
Started by the U.S. Postal Service in 1912, this is the 101st anniversary of the program.
During its three decades in Philadelphia, visitors have come to the main Post Office, now on the corner of 31st and Chestnut Streets, to peruse the letters and select a family to adopt for Christmas.
"It is really hard to choose. It seems there are a lot of stories of people losing a job," said Maureen Malachowski.
People, like Jessica Hartwell who lost her job and dropped off letters from her son and her friend's nieces.
"We're in the same situation," said Hartwell. "It's hard; it's really hard."
For newcomer, Valerie Perez, choosing can be emotional.
"Dear Santa, I am writing this letter on behalf of my neighbor and her youngest son. I've watched her over the years raise her children," she read.
Corporations like the IRS have been collecting letters since they moved into the building across the street.
"Various departments adopt families, and they take over 100 families every year. This year they took 125 families," explained Jane Maull-Kirk, USPS.
"Operation Santa" ends Friday.
The post office says they received more than 400 letters from children and families across the Delaware Valley, and visitors have answered about half of them.
With one day left, there is still time to help someone in need for the holidays.