The advent of parcel post service in 1913 was a boon to farmers, marketers, and anyone with a product who wanted to sell beyond their own doorstep. Prior to Parcel Post, shippers had two options. They could send packages through the post if they weighed less than four pounds. Anything over four pounds had to go by private express. These companies operated in cooperation, not competition, and their shipping prices were high and easily subject to change. Parcel Post service provided customers with both relatively low and standardized national prices.
The new rate encouraged sellers and buyers alike. The increased volume and variety of goods sent through the mail stream sparked a new market for mailing containers. Manufacturers answered by creating boxes and tubes specially constructed for particular goods.
Nancy A. Pope, National Postal Museum