The Boston & Maine Railroad bought twenty-five "Berkshire" type locomotives from the Lima Locomotive Works and numbered them 4000 through 4024. These B&M "Berks" had a very distinctive appearance. The feed water heaters circled the crown of the smoke box and lent a cavernous look to the front of the locomotive.

The first batch of twenty locomotives, designated Class T-1a, arrived in 1928 and had 63" diameter drivers, 27.5" x 30" cylinders, a boiler pressure of 240 psi, they exerted 66,500 pounds of tractive effort and each weighed 390,200 pounds. The last five, designated Class T-1b, were delivered in 1929 and were similar except they had a tractive effort of 68,990 pounds and a weight of 403,000 pounds.

From the beginning, the B&M had problems with their Lima built "Berkshires". The problem was with the trailing four-wheel truck. Because of the large firebox and large ash pan the locomotive had to have an articulated frame. The back end of the firebox had to rest on a moving base and it was subject to buffeting and twisting, resulting in chronic leakage at the mud ring, side sheet stay bolts and the throat sheet, as it tried to wiggle from side to side to follow the motion of the trucks. Also, this arrangement would sometimes cause the rear wheels to derail while backing up.

During the closing months of World War II, the western railroads were in dire need of motive power to handle the shift in material and personnel from the European front to the war in the Pacific. The Boston & Maine was never really satisfied with its Lima built "Berkshires" and jumped at the chance to help the war effort and to unload its "lemons". The B&M sold ten "Berkshires" to the Southern Pacific and seven to the Santa Fe.

There are no surviving B&M 2-8-4 "Berkshire" type locomotives.