Smithsonian Institution, National Postal Museum

This mailbox may look ho-hum, but when it was strapped to a missile and fired from a submarine on June 8, 1959, the only hum was that of a Regulus I missile hurtling a hundred miles with important letters in tow. That’s right—this missile was the first (and last) of an ambitious, abandoned plan to send mail across the U.S. using Cold War-era weaponry.

That weaponry wasn’t exactly in short supply in 1959. That year, despite Soviet premier Nikita Khrushchev’s visit to the United States, East and West were still in a tense stalemate. On both sides of the Iron Curtain, tons of nuclear weapons were produced, and each side had a vested interest in showing just how terrifying its arsenal could be.

Postmaster General Arthur Summerfield, who helped Dwight D. Eisenhower win the presidency, was steeped in postwar American exceptionalism. It’s no wonder, then, that he dreamed of helping the country’s abundant nuclear technology go postal. Inspired by stories of the accuracy of the United States’ new missiles, Summerfield dreamed up a way for the Post Office and the Department of Defense to collaborate to make the mail even more efficient. Why not use the fast, targeted missiles being developed by the U.S. military to deliver mail?

Summerfield’s idea wasn’t exactly new—people had been experimenting with mail delivery via rocket for decades. In 1936, an experimental rocket-powered glider delivered mail from Greenwood Lake, New York to Hewitt, New Jersey in the first successful American attempt, and the idea was repeated in Germany and other countries through World War II. And just months before this mailbox made its fateful mission, naval officers had shown off the capacities of their new guided missiles by loading them with letters.

New or not, Summerfield was determined to make an official attempt to prove that missile mail was viable. At his suggestion, a grandiose experiment was undertaken by the Post Office Department, as it was then known, and the U.S. Navy.

Two special metal mailboxes were designed to hold a total of 3000 letters and be strapped onto the side of the Regulus I missile, a formidable weapon and the United States’ first nuclear deterrent to be entirely sea-based. The 42-foot-long missile weighed about seven tons and was designed to be guided and shot from submarines.

On the assigned day, the mailboxes were stuffed with 3000 identical letters from Summerfield to a slew of dignitaries, including the president, his cabinet, each member of Congress and members of the Supreme Court. The missile was fired from the USS Barbero, one of the subs assigned to patrol the Pacific and Atlantic and threaten Soviet targets, while it was off the coast of Florida. Twenty-two minutes later, it landed at the Naval Auxiliary Air Station in Mayport, Florida, about 100 miles away [PDF].

The letters were given special postmarks, the formerly secret experiment was publicized, and missile mail was declared a success—not least because it not-so-subtly suggested that messing around with the United States’ hyperaccurate guided missile system wasn’t wise.

“Before man reaches the moon,” Summerfield gloated, “mail will be delivered within hours from New York to California, to England, to India, or Australia by guided missiles.” But he spoke too soon—apparently no serious consideration was ever given to his idea, and by the time his successor took office the idea was dead in the water. Today, one of the 11x11.5-inch mailboxes sits in the collection of the Smithsonian National Postal Museum in Washington, D.C., a reminder of the first and only time the United States used guided missile to deliver mail … and a message.