A small (late) point of clarification. Yes, the so-far-earliest known use of the idiom — in this case, “the full nine yards” — happened to appear in a blurb in a Mitchell, Indiana newspaper about who would be playing in an upcoming (amateur) baseball game, but the expression in this instance didn’t have anything to do with baseball — the game or any facet of the game — itself. The phrase was used to indicate a full player line-up, so nothing to do with literal yardage. (A month later, “the whole nine yards” showed up in a Kentucky newspaper and that text had nothing to do with baseball.)
“The Judge’s Big Shirt,” which contains the non-idiomatic usage of “the whole nine yards,” first appeared in a January 1855 issue of a Raleigh, NC newspaper, and was said to have taken place in the eastern part of the state some years before. The text was reprinted in many newspapers across the United States in 1855, but I’ve not found instances of its being republished after 1855.
Indiana and nearby Kentucky do seem to have represented a hotspot for idiomatic uses of “the whole six/nine yards” beginning ca. 1910, but the idiom shows up in Missouri, Arkansas, South Carolina, and Georgia newspapers within just a few years, which to me indicates — because of its geographical extent — that the overall form had existed for some time (decades) before it was captured in print. (Or, at least captured in print that we’re able to easily access.)
This had occurred to me, too, but I think it possible that Southern service members carried the expression into the military during WW2 and its aftermath. (I once read a paper indicating that Southerners were particularly prevalent and influential in post-war military aviation and the early years of the space program.)
Oops, sorry, I had misremembered this. The writer used “the full nine yards” with regard to a full baseball game (of nine innings), but again this had nothing to do with literal yards.