Union Pacific's Big Boy No. 4014, the largest steam locomotive in the world, is trekking across the Midwest in celebration of the 150th Anniversary of the Transcontinental Railroad. Of the 25 Big Boy locomotives built, eight still survive, and No. 4014 is the only one that is operable, after having been recently restored.
I took this video in Fairfax, Iowa on July 31, 2019.
https://vimeo.com/351431688
You can read more about the Big Boy locomotives here:
https://en.wikipedia.org/wiki/Union_Pacific_Big_Boy