Tonaya said:
usa post office :)
And the mighty
TONAYA
strikes again!
The answer is: U.S. Mail (or more precisely the Parcel Post which was founded 1913).
The parcel post regulations included the sending of “bug and bees” as well as other living 'critters' (although a “chick-fee” seems to be a myth) and prompted a number of persons to “mail” their children at a price far below that of train fare.

“With the advent of Parcel Post in 1913, some adults sent their children in the mails with postage affixed to clothing, the theory being that children were under the 50 lb. weight limit, and that it was a lot cheaper to mail them than to pay rail fares.” (Wikipedia)
“An Ohio couple named Jesse and Mathilda Beagle ‘mailed’ their 8-month-old son James to his grandmother, who lived just a few miles away in Batavia. According to Lynch, Baby James' “delivery” cost his parents only 15 cents in postage (although they did insure him for $50).” :-)
“On February 19, 1914, a four-year-old girl named Charlotte May Pierstorff was ‘mailed’ via train from her home in Grangeville, Idaho to her grandparents’ house about 73 miles away. Her story has become so legendary that it was even made into a children’s book, 'Mailing May'."
Source: Smithsonian
Note: Head of the U.S. Postal Service since February 1, 2015 is Postmaster General Ms. Megan Brennan.
Other sources:
Wikipedia - Parcel Mail in Popular Culture
Politifact – Mailing Your Noisy Children