Entitled: "Merle Alcock (Metropolitan Opera contralto) mailing a letter in New York City" shows a woman putting a letter in a U.S. Mailbox attached to a post on a street corner. A post box, also known as a collection box, mailbox, letter box or drop box is a physical box into which members of the public can deposit outgoing mail intended for collection by the agents of a country's postal service. The United States Post Office Department began installing public mail collection boxes in the 1850s outside post offices and on street corners in large Eastern cities. Collection boxes were initially designed to be hung or supported, and were mounted on support pillars, lamp-posts, telegraph poles, or even the sides of buildings. By the 1880s, these pillar boxes were made of heavy cast iron to deter theft or vandalism. As mail volume grew, the Post Office Department gradually replaced pillar mailboxes with larger free-standing models, though many of the pillar boxes continued in service as late as the 1960s. Bain News Service, 1920s.