I don't believe there is a GN Museum anywhere. The Minnesota Transportation Museum has quite a few GN items at their former Great Northern Jackson St. Roundhouse near downtown St.Paul MN.
I believe the paper archives of the Great Northern and Northern Pacific are there, donated by BN or BNSF a while back.
MTM
Hustle Muscle on (working) Turntable
This may not be what you have in mind, but the corporate records of the Great Northern Railway, Northern Pacific, and Soo Line are at the Minnesota Historical Society.
"Corporate records of the St. Paul-based Great Northern, its predecessors, and its subsidiaries and affiliates, documenting their operations across the northern tier of western states for more than one hundred years, until its 1970 merger with the Northern Pacific, the Chicago, Burlington and Quincy, and the Spokane, Portland and Seattle that formed the Burlington Northern."
Minnesota Historical Society • 345 W. Kellogg Blvd., St. Paul, MN 55102-1906 • 651-259-3000
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