The ubiquitous GPS, now taken for granted by billions of users, has a fascinating history. The GPS system design called for dozens of satellites all transmitting on the same frequency to be uniquely identified and precisely tracked with a low-cost, low-power, passive receiver. James Spilker was the architect of the signal structure that made this bold concept possible. One does not just “tune in” a GPS signal like a radio station. James Spilker’s oral history is a deeply moving story of overcoming personal adversity to conceptualize and articulate a novel design and an overall system concept that cost a fortune to implement, but, somewhat unexpectedly, spawned multiple world-wide industries. Having designed the signal structure, James started a company that built equipment to validate the operation and generate the critical orbit definition essential to GPS operation. His entire career has been dedicated to promoting GPS technologies, education, and philanthropy.