The EMD E5 was built as a 2000 horsepower (despite the "E" in the name of the locomotive series originally referring to an "Eighteen hundred" horsepower engine specification) locomotive for passenger service specifically for the Chicago Burlington & Quincy. The major difference between the E5 and its other early E-unit brothers was its stainless steel finish and distinctive fluting, specifically chosen to match the CB&Qs corrugated passenger trains such as the California Zephyr, Nebraska Zephyr and Silver Streak Zephyr.