The Louisville & Nashville Railroad bought a total of forty-two "Berkshire" type locomotives in three orders. The first order went to the Baldwin Locomotive Works for fourteen locomotives, which were delivered in 1942 and designated as Class M-1. The first ten of these locomotives, with road numbers 1950 through 1959, were assigned to freight service. The other four, with road numbers 1960 through 1963, pulled passenger trains between Cincinnati, Ohio and Corbin, Kentucky during the World War II years.

Second order was given to Baldwin, which delivered six more Class M-1 "Berkshires" in 1944. This group was assigned road numbers 1964 through 1969. All twenty of these Baldwin built 2-8-4 had 69" diameter drivers, 25" x 32" cylinders, a 265 psi boiler pressure, they exerted 65,290 pounds of tractive effort and each weighed 447,200 pounds.

Third order went to the Lima Locomotive Works for twenty-two locomotives which were delivered in 1949 and assigned road numbers 1970 through 1991. These locomotives had 69" diameter drivers, 25" x 32" cylinders, a 265 psi boiler pressure, they exerted 65,290 pounds of tractive effort and each weighed 448,100 pounds. This order was the next to last order Lima would receive for steam locomotives. The last order would come from the NYC&StL.

L&N's Class M-1 locomotives had the distinction of being the most expensive "Berkshire" type locomotives made. The designers included every improvement and feature known to the steam locomotive builder's craft.