In Buster Keaton's classic silent film The General (1927), what did the film title refer to?

Question

What 1920s silent film classic was conceived when its German director gazed upon the skyscrapers of New York from a ship?

Answer 1

A locomotive

The General (1927) told of a Southern confederate train engineer Johnnie Gray (Buster Keaton) and his passionate relationship with his own locomotive, named The General.