GN Locomotive Rosters
There are several sources for an all-time roster of Great Northern Locomotives:
For a comprehensive GN steam locomotive roster check out "Steam Locomotives of the Great Northern Railway" by Middleton and Priebe (out of print but sometimes available on Ebay, at swap meets or the GN Convention Railfair). This 544 page hardcover book is a must have for Great Northern steam fans and offers a great insight of the GN steam locomotive fleet.
For an all-time roster of all GN motive power, there is an excellent soft cover book published by the Railway & Locomotive Historical Society. The book is titled, "Railroad History 143 - Illustrated All-Time GN Motive Power Roster - Steam, Electric, Diesel & Motor Car" by Norman C. Keyes, Jr. & Kenneth R. Middleton. It was published by the R&LHS originally in Autumn 1980 and then reprinted in 1989. This book is a "must have" for the serious GN fan or historian. This book is out of print. If you look around, you can probably find a copy for sale on eBay.com or Amazon.com, or a used books seller.
Online a GN Diesel Locomotive Roster can be found on Ben Ringnalda's Great Northern Empire website.
A GN condensed all time locomotive roster can be found on the Great Northern Railway Page by Lindsay Korst.