"Katy bar the gate" origins -- Katherine Who?
Solution 1:
Three of the earliest four matches that an Elephind search of old U.S. newspapers finds refer to song lyrics. Here are those four instances. The earliest is the one cited in the posted question, from "The Radical Barbecue," in the [Alexandria] Louisiana Democrat (October 2, 1872):
We certainly have no right to complain of Town excitement last week. Two mass meetings and barbecues, given by the two political parties were of itself enough to stir up all human nature. Last Saturday was the grand day fixed here for the Radical Custom House Jubilee. For weeks the darkies here, who constitute the soul and brains of that party, have been buy making preparations and summoning their clans and their "critter cavalry". A few days previous to the day they had erected and raised a fine Pole, in front of the Court House, consecrated to Grant and three stars. Early Saturday morning the thunder of an old cracked anvil and the quahoo yells of the nation's wards were the knell of the approaching festivities. The Custom House Packet, with the Custom House colored band, U.S. Marshal Packard, in command, with the old flag triumphantly kissing the breeze of old Red, the band playing "Katie, Bar The Door," and with waving rags touched the wharf and proceeded to land her precious cargo. The following distinguished orators, candidates and office holders were the guests of the Custom House packet, Fraser, and walked ashore as the champions and bears of the day. ...
From "A Soldier's Wedding," in the Sedalia [Missouri] Weekly Bazoo (March 26, 1878):
A soldier at Leavenworth [Kansas], named Murphy, married a Miss Cooper. The Press takes of the green cloth, fits the stick under it, turns the crank and grinds out the following:
She was a darling creature fair / Of Murphy temperance fame (?) / Her ancestors all were foreigners, / And Murphy was her name.
This winsome maid had lovers many, / Whose love she did implore, / There was George and Fred and Harry, / And Ed who numbered with the score, / But when the soldier he came in, / It was "Katie bar the door."
Thus Mr. Cooper took his wife, / A buxom Irish dear, / He fenced her in with both his arms, And whispered in her ear,
"Our country's honor we'll maintain, / And encourage its upholders, / By adding to its recruiting force / A dozen little soldiers."
From an untitled item in the Indianapolis [Indiana] News (June 20, 1885):
Captain Colbert and Sergent Quigley returned last night from the Michigan City Prison, to which institution they escorted Whiting and Daniels. The prisoners gave no special trouble en route, and Whiting was cordially welcomed by the prion attaches, who will take care that he does not escape. When he came within sight of the prison walls Whiting remarked, "Well, it's Katie bar the door."
And from "An Incident of the Trip: How the President's Visit to St Paul [Minnesota] Upset the Hon. Pat Kelly," in the Monmouth [Illinois] Evening Gazette (October 12, 1887):
Mrs. Kelly is a French-Canadian, with very brilliant black eyes. "No, Mr. Kelly," she said, "you will entertain no cabinet officers, nor presidents, nor first ladies in this house while your daughter is being married like a hired girl in the house of a stranger. Behave like a father and give her the sort of a wedding she deserves, poor dear, or when your guests arrive they'll hear me sing, 'Katie, bar the door.'"
Patrick knows his wife right well, and he has learned that whenever she calls him Mr. Kelly she is beyond the influence of blarney. He stormed and scolded, but finally came down and agreed to give his daughter a good wedding.
The earliest match, from Louisiana in 1872, identifies the song as one played by an African American band at a political barbecue and pep rally. Whether it was of African American origin or not, the (hostile/condescending) white reporter covering the event seems to have been familiar with it and to have assumed that his readers were familiar with it, too.
The next match, from Missouri by way of Kansas in 1878, provides lyrics that are probably a burlesque of the original lyrics to the song. Nevertheless, it is not unlikely that the refrain "It was 'Katie bar the door'" appeared in that form in the original version and quite possibly in the same sense of "Don't let that rascal in here."
The third instance, from Indiana in 1885, simply reports the allusion to "Katie, bar the door" as a witticism by a convict about to enter prison.
And the fourth instance, from Illinois by way of Minnesota in 1887, involves a threat by a man's wife to sing the song—the threat of embarrassment evidently being due to the similarity between the situation portrayed in the original song and the real-life situation of the man, whose daughter is marrying someone against his wishes.
From these clues, I think it is likely that "Katie, Bar the Door" originated as a comic ballad, possibly in the U.S. South and certainly sometime before 1872, was popular across racial groups in the region, spread northward up the Mississippi River through the Midwest over the next fifteen years, and then extended across the entire country. The 1879 example from Lima, Ohio, in the posted question (which I did not find in my searches) fits this geographical spread fairly well. For at least a couple of decades, the expression was probably directly associated with the original song lyrics, but as memory of the song faded away, the sense of the expression as used in the song remained and became an idiom.
J.E. Lighter, Random House Historical Dictionary of American Slang (1997) includes a reference to a version of the song in Arthur Hudson, Folksongs of Mississippi and Their Background (1926–1928):
Katy, bar the door {or gate}! watch out! (used to suggest finality or impending disaster) Also it's Katy bar the door the end; disaster. {relevant citation:] 1926–28 in A.P. Hudson Folksongs of Miss. 44 {title of fiddle tune}: Katie, Bar the Door.
A look at Hudson's Specimens of Mississippi Folk-Lore (1928), however, yields only a couple of allusions to the song—as a fiddle tune played at old-fashioned dances. No lyrics appear in this text.
There is some faint possibility that the tune played in 1872 was derived from or influenced by "Get Up and Bar the Door," a very popular Scottish comic song that goes back to at least 1769. A lengthy discussion of that song (and its near variants in Scotland) appears in Francis Child, The English and Scottish Popular Ballads, volume 5 (1894). The gist of the song is that a husband and wife have a disagreement about who should shut (and bar) the door to their house and then agree that whoever speaks first should have to do it. Comic trouble ensues.
An Americanized version of the Scottish song was certainly played and sung in the United States, although how early it made the trip across the Atlantic is unclear. A version of it appears in John Cox, Folk-songs of the South (1925), with notes suggesting that it was being sung by the source's grandmother some decades before that—but as in the Scottish version, there isn't a Katie in sight (the wife's name in Cox's version is Jane).
Solution 2:
According to William Safire (NYT magazine Aug. 3, 2003) James Whitcomb Riley, a poet, in 1894 composed poem about a girl named Lide who infuriated her parents by marrying a drunkard: ''Long after she'd eloped with him and married him for shore!/When Lide married him, it was 'Katy, bar the door!'''
Solution 3:
A Confederate soldier's first person account of his wounding in 1861 contains this:
The whole country seemed to be full of Federal soldiers, and they were close and hard fighters, and when they got one of us it was said, "Katy bar the door." So you see to surrender was a thing of the past.
Reminiscences of the boys in gray, 1861-1865, Mamy Yeary, 1912.
Although the reference is anecdotal, the specific information in this part of the anecdote seems unlikely to have been contrived or misremembered.
Much has been made of the song title mentioned in the 02 October 1872 Louisiana Democrat (third column, first paragraph). This, so far, is the earliest printed record of 'Katy bar the door' that has been discovered. Along with later evidence, it appears to be the basis for a general tendency to propose that the phrase originated in lyrics or poetry.
However, given that the confederate soldier remarks the phrase in military use in 1861 with the meaning "that's the end" or "it's over", and considering also the context of the 1872 mention, a jubilatory political rally where the song was played, as well as that no record of the song title earlier than 1872 can be found, the particular tune may well have been a post-civil war creation named after or as a consequence of the sense of the phrase during the war. All told, this suggests the phrase might with equal likelihood have been adopted from a story about a specific pre-war or early-in-the-war historical event.
Somewhat later print evidence from a folk ballad tends to promote the idea that a local history lies behind the phrase and its meaning. In his "Levee Life" column, printed in the 17 March 1876 Cincinnati Commercial, Lafcadio Hearn reports the (printable part of the) lyrics of a ballad called "Number Ninety-Nine". The song was "immensely popular with the steamboatmen" (Hearn). It contained these verses:
You may talk about yer railroads,
Yer steamboats and can-el
If't hadn't been for Liza Jane
There wouldn't bin no hell.
Chorus Oh, ain't I gone, gone, gone
…
Way down de ribber road.Whar do you get yer whisky?
Whar do you get yer rum?
I got it down in Bucktown,
At Number Ninety-nine.
[Chorus]I went down to Bucktown,
Nebber was dar before,
Great big niggah knocked me down,
But Katy barred the door.
[Chorus]She hugged me, she kissed me,
She told me not to cry;
She said that I was de sweetest thing
Dat ebber libbed or died.
"Bucktown" was a rough area in Cincinnati frequented by roustabouts; "Number Ninety-Nine" was a "resort" (Hearn) in the Bucktown area.
The lyrics appear to recount a historical event, albeit perhaps a personal history, however altered and embellished in the re-telling; in the history recounted "Katy" is the lover of the 'singer'.
From the evidence presented, putting aside the possibility of simple coincidence, 'Katy bar the door' could, and probably should, be regarded as originating in or near Cincinnati, deriving from the pre-civil war or early-in-the-war events commemorated in the local ballad and perhaps in the early meaning of the phrase itself. Although "bar the door" may be an echo of transatlantic poetic influence, at least in "Number Ninety-Nine" that influence is far from direct.