First artificial satellite, Sputnik I was launched by Soviet Union on October 4th, 1957.

Soviet cosmonaut Yuri Gagarin completed the first manned space flight, orbiting the Earth in 108 minutes on April 12th, 1961.  

John Glenn became first American to orbit Earth, completing three orbits on February 20th, 1962.  

Cosmonaut Valentina Tereshkova, the first woman in space, completed 48 orbits on June 16th-19th, 1963.  

Cosmonaut Aleksei Leonov took man's first space walk on March 18th, 1965.  

Man walked on the moon for the first time. Neil Armstrong and Edwin "Buzz" Aldrin of Apollo XI spend 21 1/2 hours on the moon, 2 1/2 of those outside the capsule on July 20th, 1969.  

U.S. astronauts and Soviet cosmonauts participated in Apollo-Soyuz Test Project, docking together in space for two days on July 17th-19th, 1975.  

Challenger shuttle exploded 73 seconds after launch, killing its crew of seven on January 28th, 1986.  

Atlantis docked with Mir in first shuttle-station hookup on June 29th, 1995.  

Final US space shuttle mission ended when Atlantis arrived at Kennedy Space Center on July 21st, 2011.