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Originally and chiefly used in relation to the Wild West 1, the phrase this town ain’t big enough for the two of us, and its variants, refer to a showdown 2.
1 The expression Wild West designates the western part of the USA during its lawless frontier period.
2 Here, the noun showdown designates a confrontation serving to settle a disagreement; specifically, in the context of the Wild West, a decisive confrontation between two gunfighters.
These are, in chronological order, the earliest occurrences that I have found of the phrase this town ain’t big enough for the two of us and variants:
1-: From The Beginning and the End. The First and Last of a Desperado. A Sketch of Real Life, a short story set in Yuba County, California, published in the York County Star (Wrightsville, Pennsylvania, USA) of Friday 2nd July 1869 [page 1, column 3]:
One night, after two or three years of wild life, he [i.e., Tom Williams, the Desperado] entered a mining camp on or near the Yuba, known then as Natchez. He was, as usual, morose and ugly, ready to quarrel with any and every one, and, fixing his eyes on a young man named Jack Moore, he used a grossly insulting epithet.
The young man turned pale, deathly pale, but it was not the pallor of cowardice.
“Tom Williams,” said he, “I seek no quarrel. I do not wish to be what you are, a blood stained murderer, but unsay those words or you’ll repent having spoken them!”
“Bah! You are a coward like the rest!” cried Williams.
The next instant, his face covered with blood, he fell to the floor. Moore had taken up a two pound weight and hurled it with unerring aim at his head.
“Leave, Jack, leave!” cried the alarmed inmates of the store. “He will kill you when he comes too [sic]!”
“I will not leave; I did not seek the quarrel; I will not fly from it, or him!” said Moore, as his antagonist rose from his feet.
“I take back one thing—you are no coward!” cried Tom Williams, as he dashed the blinding blood away from his eyes.—“But look here, Jack Moore, heel yourself! [A Californian phrase—“Arm yourself.”] The world isn’t big enough for both of us. Either you or I go under in the morning. Look out for me then!”
2-: From the Wisconsin State Journal (Madison, Wisconsin, USA) of Saturday 7th October 1882 [page 1, column 5]:
Criminal Doings.
THE FRIGHTENED FORD BROTHERS.New York, Oct. 7.—Charles and Bob Ford, the slayers of Jesse James, having finished an engagement at a Broadway museum, leave tonight for Kansas City, to stand trial for participating in the murder of Wood Hite, one of the James gang, who lost his life mysteriously at the house of the Fords’ father early last winter. In a conversation, Bob Ford said: “Well, I see Frank James has come and surrendered. Now, I am curious to see what Gov. Crittenden will do. He promised me as much as that he would never pardon Frank. If he does, then I think they had better lock Frank or me up at once, for this world isn’t big enough for the two of us. If we are both at large one of us must surely be killed. Frank will never give up till he kills me, and I am sure I don’t propose to die at his hands if I stand any chance to get a first shot.”
3-: From the Petaluma Weekly Argus (Petaluma, California, USA) of Saturday 14th January 1888 [page 4, column 4]:
“FRUIT BELT RIDGE.”
(FROM OUR IRREGULAR CORRESPONDENT.)The Democrat has got a chap in these parts by the name of “Green Valleycus” […]. As I take it our constitution guarantees every man the right to seek health, wealth and happiness wherever he can find them, without scrouging on another man. But as our population has increased many fold since the above was written, its [sic] a hard thing to do. […] This is a big country, but it ain’t big enough for two such knights of the quill, and many a time in the heat of passion I have thought to send him a challenge to fight it out with four pound gloves, stuffed with sun-dried apples.
4-: From Life Among the Killers. Blood Curdling Reminiscences of a Cattle Man, published in The Kansas City Times (Kansas City, Missouri, USA) of Monday 25th February 1889 [page 8, column 5]:
“They do things queer in the west,” said a cattleman as he sat picking his teeth in the lobby of the Midland. […]
“I remember […] when Clay Allison was charging around lower Colorado. Clay was all right when he was sober but the minute he had a drink in you couldn’t call Clay real good society for anybody. On the occasion I was thinkin’ about the spring roundup was workin’ the Las Animas valley and bein’ near town a lot of the boys had gone down to West Las Animas to get drunk and loosen the boards in the dance hall floor. Well, Clay came ’round about 9 o’clock in the evening and came yelling into the dance hall whirling his gun on his forefinger like it was a pinwheel.
“‘My name’s Clay Allison an’ I want every son-of-a-gun to take off his hat here,’ he shouts, only Clay didn’t say ‘gun’ but something worse, I disremember just what now.
“Most of us pulled off our hats, and prompted by a generous public sentiment, started to laugh it off as a joke, but up gets a man, sorter pale but grum, and allowed that all the Allison’s that ever came from Tennessee couldn’t make him take his hat off. We all stopped laughing an’ stood back an’ the signs seemed about right for some one to quit this world of vain regrets right thar. But Allison, after lookin’ him over a second, says:
“‘Well, take a drink with your hat on, then.’
“We all got a drink and Allison says to the other:
“‘Bowman, this yere small state ain’t big enough for two such men as you an’ me; our trails are always crossin’ an’ one of us oughter moved a good while back. Now I’ll tell you how we’ll fix it. We’ll put our guns on the bar and get over to the other side of the room. One of the boys will give the word and the man who gets his gun first is goin’ to play in big luck an’ the other won’t be near so numerous around this dance hall to-morrow raisin’ disputes and makin’ bad blood among good quiet people.’”
5-: From chapter 26 of Her Father’s Victim. A Story of Western Life, by Thomas P. Montford, published in The Farmers’ Alliance (Lincoln, Nebraska, USA) of Thursday 28th January 1892 [page 6, column 2]:
“They’re plotting against me,” he mused, “and like as not old Scraggs has telegraphed for Blatchford, and they are going to the train to meet him. By George, I believe that old doctor is in Scraggs’ employ, and his keeping me in bed all those days was a put up job to gain time on me. I was a fool not to know that sooner. Well, if Blatchford is coming I’ve got to be going. This town ain’t big enough to hold us both.”
6-: From Run Down. The Stranger’s Call at Homesick Diggings, by ‘M. Quad’, published in The St. Joseph Sunday Herald (St. Joseph, Missouri, USA) of Sunday 15th May 1892 [page 9, column 6]:
“I’ve traveled thousands of miles while looking for Big Jim. I’ve been hunting him down, to kill or be killed. This world isn’t big enough for both of us.”
7-: From The Hartford Courant (Hartford, Connecticut, USA) of Friday 23rd December 1892 [page 4, column 1]:
When two Frenchmen decide that this little world isn’t big enough for them both they ought to retire to some quiet spot and hire a mutual friend to read them Mark Twain’s article, which did up the whole French nation in that line of busines [sic] so far as it had then been developed. In the matter of personal injury, the Deroulade-Clemenceau tragedy yesterday was of the usual French variety, but there were details that make a record worthy of publication. Six shots were fired on each side, and not even were the seconds hit.
8-: From Shooting to Kill (Founded on Fact), by ‘Volusia’, a short story set in Wyoming, published in The Atlanta Journal (Atlanta, Georgia, USA) of Saturday 19th January 1895 [page 7, column 3]:
“Every man about the neighborhood carried a heavy revolver, and mostly a winchester [sic] as well. I deemed it best, as a matter of policy, not to carry any arms at all. Even among those men a rough code of honor prevailed, and it was deemed ‘bad form’ to draw on a man who hadn’t a gun. […]
“[…]
“[…] Crockford […] flung his tumbler of whisky full in my face. Expecting something of the kind I flew from my chair and being within a yard of him I struck him a heavy blow on the mouth: he reeled back and catching a seat with his leg fell to the floor. He was on his feet in a second, revolver in hand, and I was sure that my last minute had come; and so it would have, had not Danziel seized his arm, and, by a wrench, torn the weapon from his grasp. Only just in time too, as a bullet flew past me and buried itself in the woodwork.
“‘For shame, Crocke,’ said Mottram, ‘you know that the stranger don’t carry no gun, ’twould have been murder, yes, an’ me an’ the rest of the boys would hev let you know of it too.’ A murmur of assent warned Crockford that he had transgressed the unwritten laws of frontier life. The man was deadly pale with passion, and save where the blood-stains on the lips showed the severity of the blow, all traces of color had left his usually ruddy face.
“‘Boys,’ he said, with an effort, ‘I did wrong to draw my gun and I acknowledge it, but,’ turning to me, ‘the earth ain’t big enough for us two by G–. You must fight me or I will shoot you dead on sight.’”