Garrett, you may have grabbed it by the roots. Roscoe H. is not your everyperson's model these days, but some years ago was a major influence for many. There are others not as famous.
But what we have here is the convergence/split of old and new. With a very few in the middle still. Definitely the sound originated in the Appalachian tradition - and as we envision here, a unique development of the European immigrants living in the new world. It can be traced back deep into differing sections of Europe and European folk musics. But somewhere along the line, this music became more than localized phenomenon (probably in the early 20th century and due to radio/recording) and began to typify a certain region of the United States.
Most of us now think of Ralph Stanley, Bill Monroe (and his many great vocalists!), as leading the way for Peter Rowan,Del McCourey, Mike Seegar, John Herald, and, yes, even Dan Tyminski from time to time. There are so many others with great skill at these heart-wrenching tenor vocals that showcase this style to great effect. To say they are spiritual is a bit vague, and probably not overly correct. Although some have amazing lyrical beauty, some are just plainly pathological. Yes, Gospel, Shape Note, and other religious music overlapped with the music of the many HL performers, but that's another complex story. In the modern sense, high and lonesome has now become that back of the neck hair raising sound that grabs you whether you want it to or not.
A recent commercialization that was not all that tacky was Stanley's 'O Death' in "Oh, Brother". Kind of trancended the filmed sequence.
We baritones don't always aspire to these particular heights, and tend to explore other avenues. #