Some historians trace the beginning of the Space Age to October 4, 1957, the day the USSR launched Sputnik into orbit. But, for decades prior, American men and women had been laying the engineering groundwork necessary to make the U.S. the world leader in space exploration. Through trial, occasional error, and constant determination, America has lived up to the exploratory challenges it has set for itself—from the Moon to Mars and beyond. This is the story of NASA—and the people and missions that laid the foundation for our future.