Located in the state of New Mexico (USA).
Atchison, Topeka & Santa Fe 3751 is a 4-8-4 “Northern” type steam locomotive built in 1927 by the Baldwin Locomotive Works for the Atchison, Topeka and Santa Fe Railway. Built as the first Northern type steam locomotive for the Santa Fe, the 3751 served in passenger duties until being retired in 1953. The locomotive was then placed on display in San Bernardino, California until it was restored to operating condition in 1986. The 3751 is currently located in the Central City East neighborhood of Los Angeles and is listed on the National Register of Historic Places. Today, Santa Fe 3751 holds the distinction of being the oldest surviving 4-8-4 type steam locomotive in the world. The locomotive is currently owned and operated by the San Bernardino Railroad Historical Society who use the locomotive to haul occasional mainline excursion trains. However, a 15-year inspection was expected to put it out of service for three to four years.
Source: Wikipedia