For many years, letter carriers were required to lug as much as 70 pounds of mail matter in their leather mailbags. After the advent of Parcel Post in 1913, carriers were compelled to load their satchels with all sorts and sizes of packages.
Carriers often overloaded with mail, parcel post and newspapers used wheeled hand carts to carry their mail along the daily rounds. The carts were especially useful for carrying mail retrieved from street mailboxes that began to appear in American cities in the late 1850s. Mail messengers also used carts to transfer mail between post offices and stations.