This may only be a partial history based on some quick combing of timetimes on The Museum of Amtrak Timtables website -- anybody else feel free to jump in
Empire Builder ran CHI-MSP-HVR-SEA as 7 + 8
North Coast Hiawatha ran CHI-MSP-BIL-SEA as 9 + 10
Arrowhead ran MSP-DLH as 760 + 761
In later 1977 or early 1978 the Empire Builder and North Coast Hiawatha were combined into a single daily train CHI-MSP, alternating via the Havre route as Empire Builder four days per week as 7 + 8, and via the Billings rout three days pwer week as 17 + 18
The second CHI-MSP train continued to use 9 + 10 but only ran as far as MSP and was billed the Twin Cities Hiawatha.
Arrowhead contined MSP-DLH.
The wtihn about a year in 1978 the CHI-MSP Twin Cities Hiawatha was combined with the Arrowhead to operat daily CHI-MSP-DLH using 9 + 10 and billed as the North Star. That name...and the legacy numbers 9 + 10 interited from when the second CHI-MSP train was the NCH, continued on even as the train was truncted from CHI-MSP-DLH to just being daily MSP-DLH in 1981, and then prior to being shut down in 1985 it only ran MSP-DLH on the weekends.
So there IS history of 9+10 being used on CHI-MSP even as that second CHI-MSP train no longer headed west on the NCH route. Still kind of doubtful they pull that back here, but you never know. If the NCH every does come back it's questionable if these particluar CHI departure and arrival times would be the ones continuing to (or from) the NCH routing, but who knows if that's even on their minds.
I did find it kind of cool that Amtrak did indeed for a short time use Twin Cities Hiawath for a local CHI-MKE-MSP train. Maybe history will repeat itself.
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