It's line of site and 20mi is definitely doable. Depends on terrain though. Worth a shot. And you may already have other nodes in your area.
Discussion
reasonable to start with?
https://shop.uniteng.com/product/meshtastic-mesh-device-station-edition/
So, in a valley at the base of the blue ridge, probably a no go without some outlandish antenna mount? I guess if someone was at the top of the mountain it would work? Is there a map showing networks around the US anywhere? Sorry if this is easily available somewhere, I lazily searched for at least 2 mins.