City carrier delivering packages in the snow in 1950. The carrier’s vehicle was designated to carry parcels only, not letter mail. By 1949, the post-World War II boom pushed mail volumes to unprecedented heights. A large part of the increase was in parcels, as growing families looked to mail order catalogs for more and more of their household goods. Before city carriers were assigned vehicles to carry both parcel and letter mail at the same time, parcel post deliveries were made separately.