Beginning in the mid-70s, the North Western assigned a fleet of former N&W high nose Century C628 units to its ore territory in Upper Michigan. By the late 80s, the ALCo six motor power's days were numbered. I found a great video of these locomotives in service filmed not long before their retirement:
The YouTube poster, John Pechulis Media, offers a range of DVD programs which consist of old films digitally restored utilizing advanced techinques pioneered in Europe. The results are quite remarkable.
Enjoy,
Bob