Generally speaking when I hear about the roots of country music most people point to the Scots-Irish in Appalachia which does explain a lot of country-western’s sound. However, the Irish don’t yodel and that leads to my question: how did yodeling become popular in early country music, specifically in the country-western “cowboy” music?
/u/dietdrpeppercherry provided a fine long answer, with a nice bibliography, at "When and why did yodeling, a musical technique from the Alps, become associated with the Western music of cowboys and the Great Plains?" at https://www.reddit.com/r/AskHistorians/comments/2yu0fq/when_and_why_did_yodeling_a_musical_technique/ .
Mentioning previous answers is intended as a starting point, not to discourage more discussion. Follow-on questions, info, and debate are welcome.