This is the first full-length history of the X-43 project, written by the project historian at Dryden Flight Research Center. The project achieved the first in-flight testing of a scramjet engine, at speeds of nearly Mach 7 and Mach 10. The author recorded the history as it was taking place. He received updates and documents, attended the engineering meetings, witnessed the emergency procedure training of the flight controllers, was at the flight readiness review and rpeflight briefings, and watched the third flight from one of the control rooms. After the third flight, he interviewed many of the X-34A engineers and managers about their still-fresh experiences and recollections.