This book is an overview history of the General Motors Electro-Motive Division GP7 and GP9 model diesel locomotives on the C&O. These locomotives were the backbone of C&O's first diesel fleet and were the main replacements for its freight-service steam power. Many were later used by B&O after its affiliation, and some survived into late Chessie System and early CSX eras. All were gone by the mid-1980s. They were the quintes-sential C&O freight diesel of the 1950s and 1960s. This book covers their history and presents a color album showing them at work across the system.