Gladys 6th November 2019 @ 08:06 AM I think that is the massive fish wheel that they called "Big Eddy" just up the river from The Dalles. Seeing where Mt. Hood is in the photo, it basically shows that below that fish wheel is where the Columbia started its curve. That is the one, wheel, that if people had thought about conservation, that should have been left there and maintained to give future generations at least a little look at what the "big boys" did to the river. As to the swimming hole I think it is just a slough area, that Gifford just thought looked like a swimming place. There is the possibility that it is a place that people went to swim. Looks quite calm there compared to what the main river looked like in those days……….No real way to determine where it was, as that is all under water now.