In the 19th Century, experiments in America, Europe, and elsewhere attempted to build postal rockets to deliver mail from one location to another. The idea was more novel than successful. Many stamps used in these early postal rockets have become collector's items.

CAPE CANAVERAL, Fla. -- In the Rocket Garden at NASA's Kennedy Space Center Visitor Complex in Florida, Mercury Astronaut Scott Carpenter speaks to the audience gathered for the unveiling of two new stamps that commemorate the 50th anniversary of human spaceflight from the United States Postal Service. Listening to him speak is Director of Education and External Relations for Kennedy, Cheryl Hurst (left), Center Director, Bob Cabana and United States Postal Service Official Steve Massey. One stamp commemorates NASA's Project Mercury and Alan Shepard's historic launch on May 5, 1961, aboard the spacecraft Freedom 7. The second stamp honors NASA's MESSENGER, which reached Mercury in March to become the first spacecraft to orbit the planet. The two missions frame a remarkable 50-year period in which America advanced space exploration through more than 1,500 crewed and uncrewed flights. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- In the Rocket Garden at NASA's Kennedy Space Center Visitor Complex in Florida, United States Postal Service official Steve Massey addresses the audience during an event unveiling two new stamps that commemorate the 50th anniversary of human spaceflight from the United States Postal Service. One stamp commemorates NASA's Project Mercury and Alan Shepard's historic launch on May 5, 1961, aboard the spacecraft Freedom 7. The second stamp honors NASA's MESSENGER, which reached Mercury in March to become the first spacecraft to orbit the planet. The two missions frame a remarkable 50-year period in which America advanced space exploration through more than 1,500 crewed and uncrewed flights. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- In the Rocket Garden at NASA's Kennedy Space Center Visitor Complex in Florida, a United States Postal Service poster reveals the two new stamps that commemorate the 50th anniversary of human spaceflight. One stamp commemorates NASA's Project Mercury and Alan Shepard's historic launch on May 5, 1961, aboard the spacecraft Freedom 7. The second stamp honors NASA's MESSENGER, which reached Mercury in March to become the first spacecraft to orbit the planet. The two missions frame a remarkable 50-year period in which America advanced space exploration through more than 1,500 crewed and uncrewed flights. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- In the Rocket Garden at NASA's Kennedy Space Center Visitor Complex in Florida, Laura Churchley (left), Alice Wackerman and Julie Jenkins, daughters of Mercury Astronaut Alan Shepard, speak to the audience in attendance for the United States Postal Service unveiling of two new stamps to commemorate the 50th anniversary of human spaceflight. Listening to them speak is Director of Education and External Relations for Kennedy, Cheryl Hurst (left), Kennedy Center Director, Bob Cabana and United States Postal Service official Steve Massey. One stamp commemorates NASA's Project Mercury and Alan Shepard's historic launch on May 5, 1961, aboard the spacecraft Freedom 7. The second stamp honors NASA's MESSENGER, which reached Mercury in March to become the first spacecraft to orbit the planet. The two missions frame a remarkable 50-year period in which America advanced space exploration through more than 1,500 crewed and uncrewed flights. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- In the Rocket Garden at NASA's Kennedy Space Center Visitor Complex in Florida, the audience and speakers stand for the Pledge of Allegiance and the singing of the National Anthem by a member of the 45th Space Wing Honor Guard from Patrick Air Force Base in Florida. Also on stage are, from left, Director of Education and External Relations for Kennedy Cheryl Hurst, Center Director Bob Cabana and United States Postal Service official Steve Massey, Mercury Astronaut Scott Carpenter, NASA Administrator, Charlie Bolden, Julie Jenkins and NASA's Deputy Director for Planetary Science, Jim Adams, all in attendance for the United States Postal Service unveiling of two new stamps to commemorate the 50th anniversary of human spaceflight. One stamp commemorates NASA's Project Mercury and Alan Shepard's historic launch on May 5, 1961, aboard the spacecraft Freedom 7. The second stamp honors NASA's MESSENGER, which reached Mercury in March to become the first spacecraft to orbit the planet. The two missions frame a remarkable 50-year period in which America advanced space exploration through more than 1,500 crewed and uncrewed flights. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- In the Rocket Garden at NASA's Kennedy Space Center Visitor Complex in Florida, NASA's Deputy Director for Planetary Science, Jim Adams speaks to the audience after the unveiling of the two new stamps that commemorate the 50th anniversary of human spaceflight designed by the United States Postal Service. One stamp commemorates NASA's Project Mercury and Alan Shepard's historic launch on May 5, 1961, aboard the spacecraft Freedom 7. The second stamp honors NASA's MESSENGER, which reached Mercury in March to become the first spacecraft to orbit the planet. The two missions frame a remarkable 50-year period in which America advanced space exploration through more than 1,500 crewed and uncrewed flights. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- In the Rocket Garden at NASA's Kennedy Space Center Visitor Complex in Florida, United States Postal Service official Steve Massey and Mercury Astronaut Scott Carpenter have the honor of unveiling the two new stamps that commemorate the 50th anniversary of human spaceflight. Applauding the unveiling is NASA Administrator, Charlie Bolden. One stamp commemorates NASA's Project Mercury and Alan Shepard's historic launch on May 5, 1961, aboard the spacecraft Freedom 7. The second stamp honors NASA's MESSENGER, which reached Mercury in March to become the first spacecraft to orbit the planet. The two missions frame a remarkable 50-year period in which America advanced space exploration through more than 1,500 crewed and uncrewed flights. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- In the Rocket Garden at NASA's Kennedy Space Center Visitor Complex in Florida, Mercury Astronaut Scott Carpenter, NASA Administrator Charlie Bolden, Julie Jenkins, daughter of Mercury Astronaut Alan Shepard, and NASA's Deputy Director for Planetary Science, Jim Adams, enjoy a light moment during an event unveiling two new stamps to commemorate the 50th anniversary of human spaceflight from the United States Postal Service. One stamp commemorates NASA's Project Mercury and Alan Shepard's historic launch on May 5, 1961, aboard the spacecraft Freedom 7. The second stamp honors NASA's MESSENGER, which reached Mercury in March to become the first spacecraft to orbit the planet. The two missions frame a remarkable 50-year period in which America advanced space exploration through more than 1,500 crewed and uncrewed flights. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- In the Rocket Garden at NASA's Kennedy Space Center Visitor Complex in Florida, NASA Administrator Charlie Bolden speaks to the audience in attendance for the United States Postal Service unveiling of two new stamps to commemorate the 50th anniversary of human spaceflight. One stamp commemorates NASA's Project Mercury and Alan Shepard's historic launch on May 5, 1961, aboard the spacecraft Freedom 7. The second stamp honors NASA's MESSENGER, which reached Mercury in March to become the first spacecraft to orbit the planet. The two missions frame a remarkable 50-year period in which America advanced space exploration through more than 1,500 crewed and uncrewed flights. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- In the Rocket Garden at NASA's Kennedy Space Center Visitor Complex in Florida, NASA's Deputy Director for Planetary Science, Jim Adams speaks to the audience in attendance for the United States Postal Service unveiling of two new stamps that commemorates the 50th anniversary of human spaceflight. One stamp commemorates NASA's Project Mercury and Alan Shepard's historic launch on May 5, 1961, aboard the spacecraft Freedom 7. The second stamp honors NASA's MESSENGER, which reached Mercury in March to become the first spacecraft to orbit the planet. The two missions frame a remarkable 50-year period in which America advanced space exploration through more than 1,500 crewed and uncrewed flights. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- In the Rocket Garden at NASA's Kennedy Space Center Visitor Complex in Florida, Mercury Astronaut Scott Carpenter addresses the audience during an event unveiling two new stamps to commemorate the 50th anniversary of human spaceflight from the United States Postal Service. One stamp commemorates NASA's Project Mercury and Alan Shepard's historic launch on May 5, 1961, aboard the spacecraft Freedom 7. The second stamp honors NASA's MESSENGER, which reached Mercury in March to become the first spacecraft to orbit the planet. The two missions frame a remarkable 50-year period in which America advanced space exploration through more than 1,500 crewed and uncrewed flights. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- In the Rocket Garden at NASA's Kennedy Space Center Visitor Complex in Florida, Center Director Bob Cabana addresses the audience to announce the United States Postal Service unveiling of two new stamps to commemorate the 50th anniversary of human spaceflight. One stamp commemorates NASA's Project Mercury and Alan Shepard's historic launch on May 5, 1961, aboard the spacecraft Freedom 7. The second stamp honors NASA's MESSENGER, which reached Mercury in March to become the first spacecraft to orbit the planet. The two missions frame a remarkable 50-year period in which America advanced space exploration through more than 1,500 crewed and uncrewed flights. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- In the Rocket Garden at NASA's Kennedy Space Center Visitor Complex in Florida, United States Postal Service official Steve Massey and Mercury Astronaut Scott Carpenter shake hands after unveiling the two new stamps that commemorate the 50th anniversary of human spaceflight. One stamp commemorates NASA's Project Mercury and Alan Shepard's historic launch on May 5, 1961, aboard the spacecraft Freedom 7. The second stamp honors NASA's MESSENGER, which reached Mercury in March to become the first spacecraft to orbit the planet. The two missions frame a remarkable 50-year period in which America advanced space exploration through more than 1,500 crewed and uncrewed flights. Photo credit: NASA/Kim Shiflett

CAPE CANAVERAL, Fla. -- In the Rocket Garden at NASA's Kennedy Space Center Visitor Complex in Florida, Laura Churchley (left), Alice Wackerman and Julie Jenkins, daughters of Mercury Astronaut Alan Shepard, applaud during an event unveiling two new stamps to commemorate the 50th anniversary of human spaceflight from the United States Postal Service. One stamp commemorates NASA's Project Mercury and Alan Shepard's historic launch on May 5, 1961, aboard the spacecraft Freedom 7. The second stamp honors NASA's MESSENGER, which reached Mercury in March to become the first spacecraft to orbit the planet. The two missions frame a remarkable 50-year period in which America advanced space exploration through more than 1,500 crewed and uncrewed flights. Photo credit: NASA/Kim Shiflett