One of two Class B locomotives preserved is #1575 used on an electric freight line, one of the last B's built which used a cast steel underframe. It operated in freight service across the Illinois Traction System, and later Illinois Terminal. The country's second largest interurban network was the Illinois Traction System - the McKinley lines - that stretched across much of the state of Illinois and lasted into the late 1950's. The ITS shops in Decatur were perhaps best known for the large fleet of boxcab locomotives that were designed and built entirely in-house. The earliest of these homebuilt units were the Class B's.