It is part of the GE Dash 8 Series of freight locomotives, and its wheel arrangement is of a C-C type.

Some railroads, the Chicago and North Western Railway in particular, upgraded some of their units to ~4,135 hp (3,083 kW) and designated them as C42-8.

Former C&NW units are usually identified by a grab-iron on the front nose just above the Union Pacific shield logo, and/or the "C41-8" designation on the cab side.

The final three C&NW C40-8s were built with 4,135 hp (3,083 kW), and the prior 32 units were similarly modified as well.

Although none of these units were ever officially classed as C41-8 by GE, a safety cab version was built as the Dash 8-41CW.