"It was certainly bittersweet when we lowered the flag at the old facility and raised it at the new one," said Philadelphia Postmaster Kevin McAdams.
Moving that massive operation was not easy.
"Any time you move, including your own home, the project is always much bigger when you get into it," McAdams said. "But, we're here, we're in business, we're selling stamps, and we're ready to go."
Postal officials say the move to the smaller facility was basically a business move to save on expenses.
The old building has been sold to a developer who'll convert it into office space.
Some postal customers we spoke to say it's sad to see another piece of Philadelphia history fade away.
Others say they'll get over it.
"This might be a little more convenient because it's smaller and you might not have to do as much walking," said Dhaven Certaine of Yeadon.
If you had a post office box at the old building, your number will be the same. However, you will need new key.