what was the background for delivering such speech ?
Kennedy was convinced  of the political need for an achievement which would decisively demonstrate America's space superiority. So he asked Lyndon B. Johnson to investigate whether the United States could beat the Soviet Union in putting a laboratory in space, or orbiting a man around the Moon, or landing a man on the Moon, and to find out what such a project would cost.
We choose to go to the Moon
Convinced of the political need for an achievement which would decisively demonstrate America's space superiority, Kennedy asked his vice president, Lyndon B. Johnson, in his role as chairman of the National Aeronautics and Space Council, to identify such an achievement. He specifically asked him to investigate whether the United States could beat the Soviet Union in putting a laboratory in space, or orbiting a man around the Moon, or landing a man on the Moon, and to find out what such a project would cost. 
kennedy not because it is easy but because it is hard UNANSWERABLE what is this ? "We choose to go to the Moon", officially titled as the Address at Rice University on the Nation's Space Effort, is a speech. who delivered the speech ? John F. Kennedy. when was it delivered ? 12 September 1962. how was the speech received ? Paul Burka, the executive editor of "Texas Monthly" magazine states that the speech "speaks to the way Americans viewed the future in those days. It is a great speech, one that encapsulates all of recorded history and seeks to set it in the history of our own time. Unlike today’s politicians, Kennedy spoke to our best impulses as a nation, not our worst." what legacy did it leave behind ? The successful Apollo 11 Moon landing remains an enduring legacy of Kennedy's speech. when was it delivered ? 12 September,1962.
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We choose to go to the Moon [SEP] Background
This would also be the most expensive option; Webb believed it would require $22 billion to achieve it by 1970. Johnson also consulted with Wernher von Braun; military leaders, including Lieutenant General Bernard Schriever; and three captains of industry: Frank Stanton from CBS, Donald C. Cook from American Electric Power, and George R. Brown from Brown & Root. Kennedy stood before Congress on May 25, 1961, and proposed that the US "should commit itself to achieving the goal, before this decade is out, of landing a man on the Moon and returning him safely to the Earth." Not everyone was impressed; a Gallup Poll indicated that 58 percent of Americans were opposed.