Union Pacific UP 9000. 12 coupled Steam Locomotive (4–12–2).

UP 9000 had the longest rigid wheelbase in North America.

The prototype, UP 9000, as preserved at the Los Angeles County Fairplex in Pomona, California. CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=137037 (Licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license).

Front view of UP 9000. The third cylinder and the Gresley conjugated valve gear that controls it can be seen below the smokebox. CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=137035 (Licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license).

Union Pacific UP 9000
twelve coupled (4–12–2),
Longest rigid wheelbase in
North America and…