Santa Fe 2-10-10-2 Mallet

Side view photograph of a Santa Fe 2-10-10-2

Source:

https://commons.wikimedia.org/wiki/File:Detroit_Publishing_-_New_Mallet_articulated_compound_engine_on_the_Santa_Fe_(sky_cropped).jpg

Originally from:

https://www.loc.gov/pictures/item/2016796092/

License for this picture:

https://creativecommons.org/publicdomain/mark/1.0/