Green’s Dictionary of Slang

(US) in existence, e.g. he is the craziest person out.

1857		G. Lawrence Guy Livingstone (1858) 43: Constance Brandon and Flora Bellasys—quite the two best things out.
1876		‘Dan de Quille’ Big Bonanza (1947) 285: He’s jist the durndest dog out!
1912		Bulletin (Sydney) 1 Aug. 15/2: A black pig is hard to see in the dark, an’ he goes moochin’ off so quietly that it’s the simplest thing out to lose him off camp.
1967		H.S. Thompson letter 13 May in Proud Highway (1997) 611: If the current rumor proves out.