After parcel post service was introduced in 1913, at least two children were sent by the service, with stamps attached to their clothing. The children rode with railway and city carriers to their destination. The Postmaster General quickly issued a regulation forbidding the sending of children in the mail after hearing of those examples.
In 1913 it was legal to mail children. With stamps attached to their clothing, children rode trains to their destinations, accompanied by letter carriers. One newspaper reported it cost fifty-three cents for parents to mail their daughter to her grandparents for a family visit. As news stories and photos popped up around the country, it didn't take long to get a law on the books making it illegal to send children through the mail.
Letter Carrier Delivering Mail 
In 1900, this city letter carrier posed for a humorous photograph with a young boy in his mailbag. After parcel post service was introduced in 1913, at least two children were sent by the service. Stamps were attached to their clothing, and the children rode with railway and city carriers to their destination. The Postmaster General quickly issued regulations forbidding the sending of children via mail.
Letter carrier uses his key to unlock a mail collection box mounted to a telephone pole. A postal distribution box (used by mail carriers and clerks to store mail for neighborhood delivery) and a U.S. Mail truck are in the background. Hand-colored photographic print from 1947.