"...the postal service and defense department cooperated in an experiment using missiles to carry mail in 1959. On June 8 of that year, a missile carrying 3,000 letters was fired from Navy submarine U.S.S. Barbero to a Naval station at Mayport, Florida, one hundred miles away. On hand for the service was Postmaster General Arthur E. Summerfield, who boasted that missiles would be able to speed mail across the U.S. and oversees. Among the pieces of mail carried was a letter from President Dwight D. Eisenhower..."
Source: www.postalmuseum.si.edu
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