>>1007522There's a Google Earth .kmz file or two out there that have most of the US hot springs listed. Do a search and get a few of them because nobody has a complete list.
These two guidebooks have all the good ones. Here is the Northwest edition:
https://www.amazon.com/Hot-Springs-Pools-Northwest-Original/dp/1890880086/There is also a Southwest version. They don't have the most primitive, "unknown" ones, but these books are a good start.
Picture is a G. Earth view of the hot spring in my previous reply, Rocky Canyon on the Payette River in Idaho. We have several river canyons in the state where there are one HS after another. It takes dedication and research to find the good ones. In my opinion the best ones are the hardest to get to. Hot springs bring out the best and worst in people. A two-plus mile walk usually filters out what we call the "jackholes."