A fair number of 4-4-0's lasted into the 1930's, for branchline service. Many were re-boilered which extended their service lives. Long-lived 4-4-0's in service in the '30's were found on the Southern Pacific/Texas & New Orleans, Soo Line, Canadian Pacific, Chicago & Illinois Midland, Chicago StPaul Minneapolis & Omaha (Omaha Road), Missouri-Kansas-Texas (Katy), St Louis-SanFrancisco (Frisco), Chicago Milwaukee StPaul & Pacific (Milwaukee Road), Illinois Terminal, Missouri-Illinois ("Mike 'n Ike"), Northern Pacific, Great Northern, Pennsylvania, and Kansas City Southern. Almost all were retired by the outbreak of WW II, as worn out/obsolete and good candidates for war-inspired scrap drives.
4-4-0's that survived beyond WWII into the early '50's included those of C&IM, Katy, SP/T&NO and Canadian Pacific. Most were retired in the early '50's. The Canadian Pacific was the last North American railroad to use 4-4-0's, employing #'s 29, 136 and 144 on it's Chipman-Norton, NB branchline into early 1960. So........4-4-0's were amoung the last steam locomotives still in regular service at the end of steam!!