Louisville and Nashville class M-1

The first two batches were built by Baldwin Locomotive Works during World War II. The first batch of ten (Nos. 1950–1959) was constructed in 1942. Upon arrival to the L&N, these were initially employed on high-speed freight service. The second batch also consisted of ten members (Nos. 1960–1969). These were built in 1944 and were pressed into passenger service. The third batch consisted of twenty-two locomotives built by Lima in 1949 (Nos. 1970–1991). These were the second to last class of Berkshires to be built and ordered by Lima, the last being the New York, Chicago and St. Louis Railroad S-3 Class, with the last member, No. 779, still around today. The Big Emmas proved to be the most expensive Berkshires built due to the fact that they were fitted with every refinement known to the steam locomotive builder's craft.[2] These included roller bearings, cast-steel frames and cylinders, large fireboxes, and a large boiler capacity. Upon arrival to the L&N, the M-1s lacked trailing truck booster units. However, C-2-L units were soon fitted.

The "Big Emmas" bore a strong resemblance to the Van Sweringen Berkshires, which were Berkshires designed for the Nickel Plate Road, Wheeling and Lake Erie Railway, Pere Marquette Railway, and Chesapeake and Ohio Railway, all being based on the Erie Railroad’s 2-8-4s, which also influenced the C&O’s T-1 class 2-10-4s. Both designs used 69-inch driving wheels, the same tube diameter, and the same number and size of the flues. They also had the same cylinder diameter as the Nickel Plate Road Berkshires and the Wheeling & Lake Erie K-1s. The Nickel Plate Road S-2s and Chesapeake & Ohio K-4s, the latter of which called their 2-8-4s "Kanawhas", were also equipped with roller bearings like with the Big Emmas. However, the Van Sweringen designs all had Baker valve gear, an engine wheelbase of 42 feet, a boiler pressure of 245 psi, a firebox with 90.3 square feet of grate area, and a cylinder stroke of 34-inches. The Pere Marquette and Chesapeake & Ohio Kanawhas also had a stroke of 26-inches, and the Berkshires on the Nickel Plate Road, Pere Marquette, and Chesapeake & Ohio all had 73 tubes. The Wheeling & Lake Erie K-1 Class, meanwhile had 67 tubes. The Big Emmas, meanwhile, had Walschaerts valve gear, a 42-foot 4-inch engine wheelbase, a boiler pressure of 265-psi, a firebox grate area of 90.2 square feet, 25-by-32-inch cylinders, and 62 tubes inside the boiler.

In service, the M-1s were used on all sorts of duties.[1] These included the Southland and Flamingo passenger trains between Cincinnati, Ohio and Corbin, Kentucky, fast freight trains, and coal trains around Eastern Kentucky, where they regularly hauled trains in excess of 8,000 tons.[1] At 42 miles per hour, the Big Emmas were rated at 4,503 horsepower.[3]

VMTX No. 250001, a former L&N Big Emma tender use as an auxiliary water tender for Norfolk and Western 611

Unfortunately, by the time the last batch of Big Emmas were delivered, the L&N started to invest more in diesel power. The first batch was retired by December 1950, and the final two batches were retired by November 1956, when steam officially ended on the railroad. By 1957, all of the Big Emmas had been cut up, although most of their tenders were reused for maintenance of way service on the L&N.[4][5] Some of them were eventually converted to canteens to supply extra water for steam locomotives that were used in main line excursion service such as Southern Railway 4501, Norfolk and Western 611 and 1218; Nickel Plate Road 765 and 587; Chesapeake and Ohio 2716 and 614; and Milwaukee Road 261.[6] The two tenders from Nos. 1966 and 1984 were located at the Southeastern Railway Museum in Duluth, Georgia and the Kentucky Railway Museum in New Haven, Kentucky, respectively.