Green’s Dictionary of Slang

to put oneself first, no matter what the situation.

1832		‘Cornelius Capricorn’ Speculations on the Comet 10: I must take care of number one.
1838		Dickens Oliver Twist (1966) 388: It’s your object to take care of number one — meaning yourself!
1858		Eve. Mail (London) 2 Apr. 5/5: It would appear that those at headquarters have contrived to to take care of ‘number one’.
1844		Belfast News-Letter 22 Nov. 3/2: How far Mr Tennent may be inclined to take care of number one, I cannot say.
1866		Keowee Courier (Pickens, SC) 1 Dec. 4/3: ‘Taking care of number’ [...] must include taking care of number one’ soul.
1872		‘Mark Twain’ Roughing It 89: So judiciously taking care of No. 1.
1887		Wkly Standard & Exp. (Blackburn) 31 Dec. 6/2: The calls of the present world [...] that men must ‘take care of number one’ were often given as reasons.
1892		Springville Jrnl (NY) 23 Sept. 2/4: ‘I would like to help, but it is all I can do to take care of number one’.
1905		Kansas City Gaz. (KS) 16 Sept. 3/3: ‘I promise [...] to consult my own wishes, and to look after my own interests, to so live as to keep an eye on the main chance and take care of number one’.
1914		Standard Union (Brooklyn, NY) 8 Sept. 5/1: ‘The Law of the Jungle Is Take Care of Number One’.
1929		W.R. Burnett Little Caesar (1932) 65: I got all I can do to take care of number one.
1931		Tribune (Scranton, PA) 11 Nov. 5/7: ‘They thought they were being clever and taking care of number one’.
1944		Scotsman 5 Jan. 6/3: [crossword clue] 24 Take care of number one.
1959		Illus London News 16 May 7/1: Amongst the lot the only don / Who didn’t take care of number one.
1988		Rutland Dly Herald (VT) 7 Apr. 21/2: All this praise by Reagan [...] sounds like [...] ‘Taking care for Number One’.