The one hundred and thirty-six Mountains were the most numerous of any type of steam locomotive rostered by the Illinois Central. Its first fifteen came from Alco in 1923 (#2400-#2414). In 1925, twenty-five more came from Lima (#2415-#2439) and then, in 1926, another twenty-five from Alco (#2440-#2459). To make the fifty-six new 2500 class locomotives between 1937 and 1943, the 2900's boilers were reinforced and laid on a new, single cast frame incorporating the 30" x 30" cylinders and air pump reservoir.The 2500s weigh 409,500 lbs, 280,500 lbs on their 70" drivers. They have an engine wheelbase of 42' 3" and driver wheelbase of 18' 3". With a grate area of 88 sq ft, a 437.3 sq ft firebox including two arch tubes and four thermic syphons totalling 132 sq ft, and 1,285 sq ft superheating, total heating surface was 6,450 sq ft. They were fitted with Du Pont automatic stokers from the original Lima 2-10-2s and, operating at a boiler pressure of 240 psi, delivered 78,685 lbs tractive effort.The tender held 24 tons of coal and 11,000 gallons of water. The tenders, which were from the 2900s, were comparatively small for engines of this size and the 2500s were often seen with a secondary water tender. The 2500s had a top speed of 100 mph and worked across the entire IC system hauling both passenger and freight trains into the late 1950s. In the early 1950s, like most of the 2500s, #2542 worked out of the IC’s Illinois Division freight pool based in Chicago, IL. It was retired in October 1960.
