The book was hardcover, dark blue, large (10″ x 7″) about 1″ thick. The characters in the story: Fritz, a workman who has restored a venerable steam locomotive, a boy who takes the locomotive on a trip across the United States.
The locomotive cannot stop, but can slow down for a variety of adventures, such as traveling through the New York subway, and rescuing people from a forest fire (perhaps inspired by the fire at Pestigo, WI). Upon return, Fritz announces that the “bearings are burned out,” and the final picture shows the locomotive’s diamond stack off to one side, and a deer’s skull and antlers on the wall.
This book was in my Grandmother’s home in Berkeley, California. I would have paded through it when I was six in 1949. I was overseas in the Army when she died. The house, and all the books, were sold.