 The War Production Board controlled locomotive manufacturers during World War II and had turned down Southern Pacific's order of fourteen new Daylight locomotives in 1942.Southern Pacific re-designed the new fleet based on the older GS-2s, only with 260 psi instead of 250 psi, an all weather cab, and a new GS-4 style tender.The design was finally approved, but the War Production Board reassigned four to the smaller and power-starved Western Pacific Railroad (only the tender from Western Pacific GS6/64 #484 remains).