This is a lot, I know, but we haven’t done this in a while, so – for “the whole nine yards”-obsessed – I thought it might be helpful to list the so-far earliest known idiomatic uses of “the whole nine yards” (W9Y) and “the whole six yards” (W6Y). I’ve thrown in a “whole ten yards” (W10Y), too, because it’s used in the same way, though it’s hard to know whether someone just goofed on the number or whether this was a true variant. I’ve also tacked on two possible predecessors/variants that may be of interest. (Hard to know what that “whole three yards” is all about, but there you go.)
In the end, notice how nonchalantly these writers use the expression, without feeling the need to offset the phrase with quotation marks, indicating an expectation that their readers were already well familiar with the folksy saying. Note, too, the geographical extent of the idiom by 1930 and a seeming hotspot around Indiana and Kentucky ca. 1915.
1907 (W9Y; south central IN): Full nine yards, 5/2/1907 - Newspapers.com™
1908 (W9Y; north central KY): whole nine yards, 5/15/08 - Newspapers.com™
1908 (W9Y; south central IN): The whole nine yards, June 4, 1908, The Mitchell Commercial, Mitchell, IN - Newspapers.com™
1912 (W6Y; SE KY): whole six yards, 5/17/1912 - Newspapers.com™
1912 (W6Y; SE KY): whole six yards, 6/28/1912 - Newspapers.com™
1912 (W9Y; south central IN): whole nine yards, 10/10/1912 - Newspapers.com™
1914 (W9Y; north central KY): whole nine yards, 3/27/14 - Newspapers.com™
1914 (W9Y; south central IN): whole nine yards, 11/26/1914 - Newspapers.com™
1916 (W6Y; north central KY): whole six yards, 4/13/16 - Newspapers.com™
1917 (W6Y; north central AR): whole six yards, 3/23/1917 - Newspapers.com™
1921 (W6Y; NW SC): The whole nine yards - Wikipedia
1922 (W6Y; north central GA; beginning of second column): The News-herald. (Lawrenceville, Ga.) 1898-1965, March 30, 1922, Image 1 « Georgia Historic Newspapers
1922 (W9Y; north central KY): whole nine yards (typo, whos), 9/29/22 - Newspapers.com™
1923 (W9Y; north central KY): whole nine yards, 6/1/23 - Newspapers.com™
1927 (W6Y; south central MO): whole six yards, 12/15/1927 - Newspapers.com™
1930 (W10Y; north central OK): "The whole ten yards" - Newspapers.com™
Possible prototypes/variants:
1850 (“nine yards,” two uses; E MO): "Your last 'nine yards'" (possibly prototype), 12/4/1850 (another exx. in text) - Newspapers.com™
1882 (W3Y; central NC): Orange County Observer, Hillsborough, NC, 4 November 1882, p. 2 - Newspapers.com™