The United State Steel Corporation bought the Duluth, Missabe & Northern Railway and the Duluth & Iron Range Railroad in 1901 and operated them as two separate entities with both railroads carrying iron ore from the mines in Minnesota to Lake Superior.

In 1913, the D&IR gave an order to the Baldwin Locomotive Works for four "Mikado" type locomotives. It also gave the Lima Locomotive Works an order for two of the same. The six 2-8-2s arrived in 1913 and were designated as Class N with the four that Baldwin built assigned road numbers 300-303 and the two Lima built were given numbers 304 and 305.

Three more 2-8-2s were added to the D&IR roster in 1916. This Lima built group was designated as Class N-1 and were numbered 306-308.

Another three "Mikados" were delivered from Baldwin in 1923. These locomotive were very similar to the Class N-1, but weighed 27,400 pounds more.

The two railroads were operated independently, but in 1930 they combined the rosters of the motive power. The locomotives of the D&IR were renumbered simply by adding a numeral "1", as a prefix, to all existing road numbers. In 1937, the D&IR and the DM&NR were consolidated with the Spirit Lake Transfer Railway and the combined railroad was named Duluth, Missabe & Iron Range Railway.

By the late 1950s, most railroads had converted to diesels, but the DM&IR wanted to continue with steam. Between 1958-1962 it bought 26 "Mikados" from another US Steel owned railroad, the Elgin, Joliet & Eastern. These locomotives were divided into three classes, Class N-4, all built by ALCO (road numbers 1312- 1321), Class N-5, all built by Lima (road numbers 1322-1325) and Class N-6, all built by Baldwin (road numbers 1326-1337).

There is one surviving D&IR 2-8-2 "Mikado" type locomotive. It is a Class N-6, number 1330, which was ex EJ&E number 765. This locomotive is on display at City Hall at the corner of Rte 20 and Rte 53 in Gary, IN.