Space race

Main article: Space Race
Following the Soviet space program's launch of the world's first human-made satellite (Sputnik 1) on 4 October 1957, the attention of the United States turned toward its own fledgling space efforts. The U.S. Congress, alarmed by the perceived threat to U.S. security and technological leadership (known as the "Sputnik crisis"), urged immediate and swift action; President Dwight D. Eisenhower and his advisors counseled more deliberate measures. Several months of debate produced agreement that a new federal agency was needed to conduct all non-military activity in space.
Explorer-I, officially Satellite 1958 Alpha (and sometimes referred to as Explorer 1), was the first Earth satellite of the United States, having been launched at 10:48pm EST on 31 January 1958. On 29 July 1958, President Dwight D. Eisenhower signed the National Aeronautics and Space Act, establishing the National Aeronautics and Space Administration (NASA). When it began operations on 1 October 1958, NASA consisted mainly of the four laboratories and some 80 employees of the government's 46-year-old research agency, the National Advisory Committee for Aeronautics (NACA). A significant contributor to NASA's entry into the Space race was the technology from the German rocket program, led by Wernher von Braun, who became a naturalized citizen of the United States after World War II. He is today regarded as the father of the United States space program. Elements of the Army Ballistic Missile Agency (of which von Braun's team was a part) and the Naval Research Laboratory were incorporated into NASA.

May 5, 1961 launch of Redstone rocket and NASA's Mercury Freedom 7 with Alan Shepard Jr. on the United States' first manned sub-orbital spaceflight.
NASA's earliest programs involved research into human spaceflight and were conducted under the pressure of the competition between the USA and the USSR (the Space Race) that existed during the Cold War. The Mercury program, initiated in 1958, started NASA down the path of human space exploration with missions designed to discover simply if man could survive in space. Representatives from the U.S. Army (M.L. Raines, LTC, USA), Navy (P.L. Havenstein, CDR, USN) and Air Force (K.G. Lindell, COL, USAF) were selected/requested to provide assistance to the NASA Space Task Group through coordination with the existing U.S. military research and defense contracting infrastructure, and technical assistance resulting from experimental aircraft (and the associated military test pilot pool) development in the 1950s. On May 5, 1961, astronaut Alan B. Shepard Jr. became the first American in space when he piloted Freedom 7 on a 15-minute suborbital flight. John Glenn became the first American to orbit the Earth on 20 February 1962 during the 5 and a quarter-hour flight of Friendship 7.
Once the Mercury project proved that human spaceflight was possible, project Gemini was launched to conduct experiments and work out issues relating to a moon mission. The first Gemini flight with astronauts on board, Gemini III, was flown by Virgil "Gus" Grissom and John W. Young on 23 March 1965. Nine other missions followed, showing that long-duration human space flight was possible, proving that rendezvous and docking with another vehicle in space was possible, and gathering medical data on the effects of weightlessness on human beings.

from http://en.wikipedia.org/wiki/Nasa