Human spaceflight is the driver for most activities that the National Aeronautics and Space Administration (NASA) undertakes. While NASA certainly has a rich aviation research heritage and has also done pathbreaking scientific and applications work using robotic spacecraft, human spaceflight is a difficult and expensive endeavor that engenders great popular enthusiasm and support for NASA. Much of this public interest stems from pushing boundaries of adventure, by exploring the unique and challenging physical environment of space. Humans can also perform tasks in space that machines cannot. We can think, analyze, and make judgment calls based on experience and intuition in real time. This NASA history document contains sixteen fascinating essays about the past and future of spaceflight, written by some of the most important and famous figures in the space community. A confluence of anniversaries made the spring of 2001 a propitious time for reflection on a forty-year record of achievement and on what may lie ahead in the years to come. The fortieth anniversary of Alan Shepard's first spaceflight, the first time an American flew in space, took place on 5 May 2001. The fortieth anniversary of Yuri Gagarin's spaceflight, the first time a human traveled into space and orbited Earth, took place on 12 April 2001. Coincidentally, this date was also the twentieth anniversary of the launch of STS-1, the first Space Shuttle flight. In addition, 25 May was the fortieth anniversary of President John F. Kennedy's famous "urgent needs" speech in which he proposed putting an American on the Moon "before this decade is out," initiating the Apollo Project. Last but not least, the Expedition One crew to the ISS had finished its historic first mission in the spring of 2001.