The Soviet Union launched Sputnik 1, the first artificial satellite, into orbit on October 4, 1957.

Yuri Gagarin, a Soviet cosmonaut, became the first human to travel into space on April 12, 1961.

The United States achieved the first manned moon landing on July 20, 1969, with Neil Armstrong and Buzz Aldrin becoming the first humans to walk on the moon.

Salyut 1, launched by the Soviet Union in 1971, was the first space station to be placed into orbit.

Mariner 4, launched by NASA in 1964, was the first spacecraft to successfully fly by Mars and return images of the planet.

The Space Shuttle, developed by NASA, was the first reusable spacecraft to be used for human spaceflight.

The United States launched Syncom 2, the first geostationary communications satellite, into orbit in 1963.

The Hubble Space Telescope, launched by NASA in 1990, was the first major optical telescope to be placed into orbit.

The Soviet Union launched Venera 3, the first spacecraft to reach Venus, in 1965.

Galileo, launched by NASA in 1989, was the first spacecraft to successfully orbit Jupiter and send a probe into its atmosphere.

The United States launched Pioneer 11, the first spacecraft to visit Saturn, in 1973.

Viking 1, launched by NASA in 1975, was the first spacecraft to successfully land on Mars and return images and data from the planet's surface.

The United States launched Voyager 2, the first spacecraft to visit Uranus, in 1986.

Cassini-Huygens, a joint mission between NASA and the European Space Agency, successfully landed the Huygens probe on Titan in 2005.

The United States launched New Horizons, the first spacecraft to visit Pluto, in 2006.