'Big Boy'.

 

Brand new and gleaming Union Pacific 4884-1 class "Wasatch" number 4000. Better known as a "Big Boy" thanks to a worker and a piece of chalk, the massive 4-8-8-4 simple articulated was built by the Schenectady plant of the American Locomotive Company, construction number 69571, in August of 1941. Number 4000 was photographed undergoing initial testing, and the dynamometer car can be seen behind the tender. After the final service runs in June of 1959, the locomotives were retired and temporarily stored. Eight "Big Boy" locomotives were eventually preserved, and in 2019, number 4014 was restored to service by the Union Pacific for the 150th anniversary of the completion of the first Transcontinental Railroad.