Answer: Mail

In the 1950s, the Post Office Department (predecessor of the United States Postal Service) and the U.S. Navy entered into an interesting but short-lived arrangement. A Post Office was established aboard the USS Barbero, and a Regulus cruise missile, traditionally tipped with a nuclear warhead, was outfitted with two special containers to hold mail.

3,000 pieces of mail, entirely a collection of postal covers addressed to government officials like President Eisenhower and Post Masters across the nation, were launched from far out at sea and delivered via the missile to a predetermined land-based target. Not only did the missile hit the target dead on but the mail was successfully retrieved.

Although Post Office officials declared it a new age in mail delivery, the June 1959 delivery of “rocket mail” was to be the only one. In reality, the Navy knew it would never be cost efficient to delivery mail via rocket, but the collaboration with the Post Office gave them a perfect opportunity to show off the precision of U.S. sea-to-land nuclear missiles to the world under the auspice of delivering mail.