6400 in particular is the most famous and notable, having pulled the 1939 royal train, and participating as an attraction at the New York World's Fair the same year.

The locomotive was eventually donated and put up on static display in the National Museum of Science and Technology in Ottawa, where it has been preserved since 1967.

Intended for passenger service, primarily in southern Ontario and Quebec, these locomotives, with their sleek modern style, also became an important marketing tool for the company.

It also remains the only sole surviving and preserved member of the U-4-a Class 6400 series, as sister locomotives 6401-6404 were retired and scrapped in the early 1960s.

No examples of this subclass have survived into preservation, as they were all retired and scrapped, presumably from 1960 to 1961, when dieselization was common place on most major American railroads.