Pennsylvania Railroad S1 6–4–4–6.

Largest Passenger Locomotive Ever Constructed.

The official publicity photo of PRR S1 6100 of 1939. By University of Southern California Library/California Historical Society — link University of Southern California Library/California Historical Society, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=58341376 (Licensed under the Creative Commons Attribution 3.0 Unported license).

Detail of the cylinders and driving wheels of Pennsylvania Railroad S1 6–4–4–6 steam locomotive at the New York World’s Fair, July 15, 1939. Original uploader was Morven at English Wikipedia. — Transferred from en.wikipedia to Commons by SchuminWeb using CommonsHelper., Public Domain, https://commons.wikimedia.org/w/index.php?curid=8902319

PRR S1 #6100 hauling the Trail Blazer, PRR’s premier, luxury all-coach train between New York and Chicago in Nov 1942. Notice fairing removed to aid in maintenance. Picture by PRR1944 — Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=72839502. Licensed under the Creative Commons Attribution-Share Alike 4.0 International license.

PRR S1 №6100
“The Big Engine”,
Only 1 ever made,
Experimental duplex locomotive,
Intended to demonstrate
duplex drive advantages
according to opinions of
Baldwin Locomotive Works.

Longest and heaviest
rigid frame reciprocating
steam loco ever built,
Streamlined Art Deco
locomote faring by
Raymond Loewy.

Configured as 6–4–4–6
Duplex drives,
Two pairs of cylinders
each driving two pairs
driving wheels,
High speed stability
required rigid frame
no articulation,
S1 №6100 completed on
January 31, 1939.