10048 was the ZIP code assigned to the original World Trade Center complex in New York City. It was discontinued following the September 11 attacks in 2001. Years afterward, mail continues to be sent to 10048 by senders who have not updated their mailing lists. The ZIP code is being kept active by the United States Postal Service (USPS). It has not been assigned to 1 World Trade Center and other buildings planned for the World Trade Center site, which use the ZIP code 10007 instead.
Before the September 11, 2001 attacks, there were eight letter carriers assigned to the buildings to deliver mail to the buildings' tenants. All of the Postal Service employees survived the attacks. In the months following the September 11, 2001 attacks, over 80,000 pieces of mail continued to arrive each day addressed to the World Trade Center, including some items loosely addressed to such recipients as "The Search Dogs" or "The Rescuers". As of 2003, 3,600 items of mail per day were still being sent to 10048. These items were processed at the James A. Farley General Post Office, the main facility for New York City, located across from Penn Station in Midtown Manhattan. Mail there was held for pick-up by messenger, forwarded to the intended recipient, returned to its sender, or destroyed. Following the attacks, the United States Postal Service provided free mail-forwarding service to the WTC's former occupants for three years, rather than the usual one-year period. By the end of 2006, the number of items sent to 10048 had decreased to around 300 items daily, mostly sent from businesses and organizations that had not yet updated their bulk mailing lists.
The 90 Church Street Station Post Office building is located adjacent to the World Trade Center site and the PATH station.
The 10048 ZIP code was used again after the September 11, 2001 attacks for a pictorial cancellation commemorating the anniversary of the attacks.