The Portland section of Amtrak's Empire Builder passes across the Columbia from Cascade Locks, Oregon, on its morning run to the City of Roses. I was told that the bare mountainside in the background was caused by a huge slide that damned up the river and created the rapids that needed locks built around them for river boats to get through. Apparently Lewis and Clark encountered many dead trees in the area inundated by the new lake behind the slide, so apparently the slide happened in relatively modern times, say the the 1600's, as opposed to thousands of years ago.
The famed natural aspect of the Pacific Northwest has drawn tourists and railfans alike from all over the world. This photo compilation showcases the sections where rails meet water between Washougal, WA/Troutdale, OR and Plymouth, WA/Boardman, OR.