First trip to Washington?

We've been trying to determine when the 5057 made its first trip to Washington by looking through dispatcher train sheets in our archival collections.  These documents were the official 'diary' of what happened within the train dispatcher's territory during a particular day.

Cascade Rail Foundation has an extensive collection of these documents for the Pacific Coast Railroad (later part of the Burlington Northern), which the Milwaukee Road used as part of its transcontinental mainline between Maple Valley, WA and Black River (south of Seattle).

Knowing that the 5057 was originally number 388 when it was built and delivered to the Milwaukee Road during the summer of 1965, we went through the dispatcher train sheets for that period.  The earliest sheet we've found that shows the 388 on a train was from July 31, 1965.  An excerpt can be seen below, with the entry for the 388 highlighted in orange.

Click to enlarge.

According to this train sheet, the 388 passed Maple Valley, WA at 12:23 a.m. pulling 2,915 tons (25 loads and 58 empty cars) with three other U25B locomotives.  It then passed Black River at 12:50 a.m. on the way to Tacoma. It would have passed through Cle Elum sometime on July 30.

Unless new information becomes available, we consider this to be the first trip of the 5057 to Washington.