You can access the river from salmonberry road and following the train tracks down. You will have to cross the river to get to the tracks. It's about five miles down to the Nehalem river from the crossing. There is not any access points below the crossing, so plan on a long pack. You can also access the tracks from beaverslide road a couple of miles upstream of the crossing. There are a fair number of elk rifle hunters that hunt this area. Some have built custom carts to run on the tracks

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Dislaimer: Railroad tracks are private property and dangerous to walk on( and probably against the law).