Three years after purchasing the four RS-3s, CN bought for GTW two turbocharged, 1000-hp RS-1s, powered by 6-cylinder 539 engines and equipped with steam generators. They were built by ALCo and delivered in October 1957 as GTW 1950-1951 (MR-10e). These were the last RS-1s built in the U.S. for a U.S. railroad (after 17 years of continuous production). They had exposed carbody filters (introduced in 1954) instead of louvers and a small two-inch lip at the top of the hood ends. They also had two sets of horns on the top of the cab roof (it must have been noisy inside the cab!).