After reading it with attention focused on lines west, the prize for unlikely routings should go to the Denver<>Rapid City<>Twin Cities route. Abandonments have Balkanized the area and on the east end of South Dakota it was too easy to build track, so everyone in the 19th century did just that.
I'm open to corrections, but here's what it seems to be made of:
From Denver via Fort Collins to Cheyenne on former Colorado & Southern. [ColoRail may propose running this line via Greeley on former Denver Pacific.]
Cheyenne to Sidney on UP Main Line.
Sidney to Crawford on former Burlington.
Crawford to Wolsey via Rapid City and Pierre on former North Western.
Wolsey to Mitchell on former Milwaukee Road.
Mitchell to Sioux Falls via Canton on former Milwaukee Road.
Sioux Falls to Twin Cities on former Great Northern.
Several of the junctions would require construction to permit head-on movements.
Competing DEN<>MSP travel could include the Denver<>Billings<>Twin Cities routing and the Denver<>Omaha<>Twin Cities routing. Those are traditional. and were available into the 1960's.
