The compact and reliable No. 1251 served for 45 years in the Reading Locomotive Shops. Known as a roundhouse "goat," the No. 1251 was an industrial switching engine used to move locomotives in and out of the shops and carried "Reading Locomotive Shops" on the tank sides. Since the Reading shops built more than 620 completely new locomotives and rebuilt hundreds of others, No. 1251 was kept busy for many years.
The Class B-4a switcher was rebuilt in 1918 from a Class I-2a Consolidation utilizing the shortened boiler, frame, drivers (minus rear set), rods, cross-heads and cylinders. The switcher was designed with the water tank and fuel bins on the locomotive itself, adding more weight for traction. Compact in size, these engines were perfect for work around industrial areas and shops.
No. 1251 was the last steam locomotive in ICC service on a Class I railroad before being retired in February, 1964. It can be seen at the Pennsylvania Railroad Museum, Strasburg, Pennsylvania.