I am mainly talking about the Oregon side. From Grants Pass to a little after Cave Junction. I know they have LTE there as I was on US Cellular just under 2 years go. I have family on the coast and take 199 often. I know where US. Cellular has LTE and EVDO along that road. Neither of which I have been ever able to connect to. However, south, north and east of Grants Pass I have gotten EVDO roaming.
Both of your maps only show half of US199.
Edit: I see how my wording was confusing and I am sorry for that.