It is a beginning. Over forty-five years have elapsed since the X-15 was conceived 40 since it first flew. And 31 since the program ended. Although it is usually heralded as the most productive flight research program ever undertaken, no serious history has been con-assembled to capture its design, development, operations, and lessons. This monograph is the first step towards that history. Not that a great deal has not previously been written about the X-15, because it has. But most of it has been limited to specific aspects of the program pilot's stories, experiments, lessons-learned, etc. But with the exception of Robert S. Houston's history published by the Wright Air Development Center in 1958, and later included in the Air Force History Office's Hypersonic Revolution, no one has attempted to tell the entire story. And the WADC history is taken entirely from the Air Force perspective, with small mention of the other contributors. In 1954 the X-1 series had just broken Mach 2.5. The