The star of this 1929 early talkie is the Santa Fe Railway's #1378 Pacific type steam locomotive. Built by the Baldwin Locomotive Company in 1912-13, it is one of 52 identical Pacifics of the 1337 Class (#1337-1388). All were retired and scrapped by 1954 with #1378 being gone before 1950.
The Santa Fe's LA railroad yards depicted here remain in use with even the long obsolete steam engine turntable still in use by Amtrak.
All through the film the kids correctly use the word Run (to operate the locomotive), not the British term Drive as sometimes erroneously heard in films.
At one point Farina says he plans to change his name to George and become a Pullman car porter. The Pullman Company hired exclusively African-Americans as porters and despite long hours and time away from home, being a Pullman Porter was long a pathway to black middle-class and home ownership. Pullman porters were all called "George" after company president George Pullman.