a time-book belonging to pennsy engineman byron breininger from the ft. wayne division records a trip to chicago on s1 engine #6100 at 8:59 am on may 5, 1946, this run was possibly one of its last in service. less than two years later, prr president martin w. clement announced that “by may of this year (1948) we expect all of our through passenger trains west of the electrified territory to be dieselized”. preservation of s1 was discussed inside prr's board, but due to the deteriorating financial situation since 1946, s1 #6100 was scrapped in 1949. the prr continued developing the t1 class of 4-4-4-4 duplex locomotives but wheel slip and mechanical failures also plagued the t1.