The Great Northern Railway M-1 was a class of 35 American 2-6-8-0 locomotives introduced in 1910. A total of 35 of these Mallet locomotives were built by Baldwin Locomotive Works in two batches; the first 10 in December 1909, followed by a further 25 in June to August 1910.^[1] They were early articulateds and worked their entire life on the Great Northern Railway (GN). These engines were unusual because of having two uneven sets of driving wheels; the front set having six driving wheels, and the rear set having eight driving wheels.

All M-1's were converted to be simple-expansion cylinders from 1926 to 1927 and reclassified M-2. Twenty-two of the M-2's were dismantled between 1929 and 1931, with parts being recycled into new class O-7 Mikados numbered 3376-3396 in 1930 . Three O7 Mikado's were rebuilt to O8 Mikados numbered 3397-3399 in 1932 . The 13 M-2's not rebuilt lasted until the dieselisation era, and were sold for scrap between 1949 and 1954. No M-1's have survived into preservation. None of the O-8's that were rebuilt from the O-7's that were once part of the M-1's were preserved either.^[2]

• [1] as M-1.
• [2] as rebuilt to M-2.

• Keyes, Norman C. Jr.; Middleton, Kenneth R. (Autumn 1980). "The Great Northern Railway Company: All-Time Locomotive Roster 1861-1970". Railroad History (143). Boston, Massachusetts: The Railway and Locomotive Historical Society, Inc. ISSN 0090-7847.