Hard to tell about Lewis and the flood plain. It's near Forest City. Have a look at Google maps. Craig is further north, but about the same distance from the river. What you can't see is how the terrain changes. Never been there.
You'll find the Holt Hist Soc very helpful. They have transcriptions of all the newspapers, indexed by name, from 1857 to after 1900. The publishers seem to have put everybody in the paper once a week to keep people buying the paper. It has been a treasure trove for my research.
Bottoms refers to the lands that we would today called wetlands bordering the river. Easy fishing and small game hunting. Mostly gone today due to levies and other flood and erosion control programs.