What does "in transit" mean at USPS?

When a package is in transit with USPS, it means that the delivery is currently traveling through the postal transportation network. USPS Tracking, a free service, can display the last known location of a package within the USPS system.

Some shipments are not scanned at every location along the way, so a package that is being transported over long distances may not have tracking information available until it arrives at the Post Office closest to the recipient. Delivery information about a USPS package typically displays the time and date of delivery and information about where it was placed or received.