End of the steam locomotive era. With the advent of the diesel-electric locomotive in the twentieth century, the decline of the steam locomotive became a reality. The diesel-electric locomotive took hold by the 1930s, and by the 1950s, the full transition from steam power in North America was complete. The romantic nature of the steam locomotive mainly exists now in train museums and various steam locomotive lines catering to tourists who want to relive the great steam era. This book is designed to give a simple understanding of how these great steam locomotives worked.