July 2019 marks 50 years since Neil Armstrong took his famous first steps on the surface of the Moon. As people around the world celebrate the anniversary of this great American achievement, they might wonder why there have been no further human missions to the Moon since Apollo 17 in 1972. This book assesses the legacy of the Apollo missions based on several decades of space developments since the program’s end. The question of why we haven’t sent humans back to the Moon is explored through a multidisciplinary lens that weaves together technological and historical perspectives. The nine manned Apollo missions, including the six that landed on the Moon, are described here by an author who has 50 years of experience in the space industry and whose work spanned the Apollo 8–13 missions. The final section of the book provides a comprehensive assessment of today’s programs and current plans for sending humans to the Moon.