The Boston & Albany Railroad was the first railroad to test Lima's 2-8-4 "superpower" design and it was impressed enough to immediately order twenty-five of the new locomotives. The B&A was the first railroad to use the 2-8-4 and it gave this wheel arrangement its name "Berkshire" for the Berkshire Hills where it was tested.

The first order was for twenty-five exact duplicates of the demonstrator that was used in the tests. This group arrived from the Lima Locomotive Works in 1926 and was designated Class A-1a and assigned road numbers 1400 through 1424. These first production "Berkshires" had 63" diameter drivers, 28" x 30" cylinders, a boiler pressure of 240 psi, they exerted 69,400 pounds of tractive effort and each weighed 389,000 pounds.