Union Pacific 'Challenger' Project Reference  


The Challenger Locomotives

William W. Kratville

William W. Kratville © 1980

 

Union Pacific Steam - Challenger Portraits

 James L. Ehernberger

Challenger Press © 1993

 

Union Pacific Prototype Photos Volume #36 (4-6-6-4 Challenger)

Union Pacific Historical Society

ISBN#: 978-1-932704-28-0

 

Union Pacific Prototype Photos Volume #37 (4-6-6-4Challenger)

Union Pacific Historical Society

ISBN#: 978-1-932704-29-7

 


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