Up until the 1990s, there were three railways serving the Ottawa Valley:
- The CP Chalk River Sub, which made up part of the original Transcontinental route from Montreal to Vancouver (Port Moody). with stops in Pembroke, Renfrew, and Arnprior. It was pulled up between Mattawa and Smiths Falls in 2012.
- The CN Beachburg Sub, which was the old Canadian Northern Line. It went from North Bay through the north part Algonquin Park to Pembroke and Beachburg, across the Ottawa River to Quebec for a bit, then back across into Ontario to Ottawa. Between North Bay and Pembroke, it was abandoned in 1995, from Pembroke to Ottawa, rails were pulled up in 2015.
- The CN Renfrew Sub, which was the old Canada Atlantic Railway between Ottawa and Depot Harbour (near Parry Sound), which later became part of the Grand Trunk system. It went through the south part of Algonquin Park, stopping at Eganville, Renfrew, and Arnprior. It was abandoned in stages from the 1930s through the 1990s, though a small part remains in use to serve industry in Arnprior.