^^ that's 'Big Boy' ^^ 4014
https://en.wikipedia.org/wiki/Union_Pacific_4014Built in 1941 by the American Locomotive Company (ALCO) of Schenectady, New York, No. 4014 is the only operating Big Boy of the eight that remain in existence. Around 9 p.m. on May 1, it moved under its own power for the first time in more than 59 years. The following evening, the locomotive made its first test run: a round trip from Cheyenne to Nunn, Colorado.