The PRR J1 was a class of 2-10-4 "Texas" type steam locomotives built between 1942 and 1944.

Other changes to the driving wheels included counterbalancing, as it was found in service that the J1s ran roughly like their T-1 counterparts.

The engine had lateral motion devices to allow sideways drive axle travel which did enable it to work on PRR curves.

Other changes included the curved front side cab windows and the cast pilot with drop coupler.

A total of 125 were built at PRR's shops in Juniata, Pennsylvania; the later 60 locomotives were classified as the J1a.