This book attempts to delineate the history of the Martin P4M Mercator. It is not by any means a complete narrative, due to the secret nature of the Mercator's career and its importance to the Cold War. Through mishaps and shoot-downs, the nineteen ship production run flew clandestine electronic intelligence missions against China, North Korea, Russia, and Vietnam until 1960. Many of the documents, drawings and photos used in this book were declassified for this publication as late as 6-17-96. Even so, I trust that all that acquires this book will thrill at the beauty and gracefulness of the big Martin.