The Illinois Central Railroad bought fifty "Berkshire" type locomotives from the Lima Locomotive Works in 1926. They were designated as Class A-1 and numbered 7000 through 7049. Numbers 7000 through 7039 had Elesco feed water heaters and numbers 7040 through 7049 had Worthington BL feed water heaters. The IC then purchased the Lima A-1 demonstrator and numbered it 7050. This is the very same demonstrator that was tested in the Berkshire Hills for the Boston & Albany and later went on the road to sell this new class of locomotive for Lima.

These superpower locomotives designed and tested for rugged mountainous service on heavy grades were used on a nearly flat division of the Illinois Central. These locomotives had 63 1/2" diameter drivers, except number 7050 had 63" diameter drivers, 28" x 30" cylinders, a boiler pressure of 240 psi with a resultant tractive effort of 68,850 pounds (69,400 pounds for number 7050). Each weighed 388,000 pounds except number 7050 weighed 385,000 pounds. These Class A-1 locomotives provided the inspiration for the Paducah sandbox on the number 2500 through 2600 4-8-2s and later versions of locomotives in the fleet.

As the Paducah, KY shops embarked on the rebuilding program in 1937, they converted #7038 into a 4-6-4 Hudson with the intent to convert all 2-8-4s to this wheel arrangement for use in high speed merchandise freight service. This locomotive was numbered 1 until 1945 when it was renumbered 2499. It was scrapped in 1950. As this was one of the few failures from Paducah they upgraded the remaining locomotives as 2-8-4s and renumbered them 8000 through 8049. The IC called them "Limas", but the enginemen called them "Big Mikes". These 2-8-4s lost their most Lima-distinguishing characteristic, the feed water heater that hung over the brow of the smoke box door. With this change and some others these locomotives assumed the standardized look and design of Illinois Central motive power.

The rebuilds provided the railroad with locomotives that weighed 393,000 lbs and had 63 ½" diameter drivers, 27" x 30" cylinders and exerted 77,578 pounds of tractive effort under 265 psi of boiler pressure.

There are no surviving IC 2-8-4 "Berkshire" type locomotives