Green’s Dictionary of Slang

of a person, most important, most central or authoritative in an organization.

1905		Wash. Post 15 Jan. 4/4: Larry Summerfield, the king-pin wire-tapping faker of them all.
1916		Tomahawk (White Earth, Becker Co., MN) 19 Oct. 3/5: Sure, he’s the king-pin rustler.
1929		J. Lait Broadway Melody 21: Zannie — the kingpin producer o’ the whole world.
1938		H. Asbury Sucker’s Progress 400: Carney and Glassford were the king-pin gamblers of Buffalo.
1949		Aberdeen Jrnl 12 Mar. 2/2: It’s Funny! It’s Melodious! It’s Terrific! with Eire’s King-pin Comic.
1952		(con. 1920s) ‘Harry Grey’ Hoods (1953) 164: He was the kingpin hoodlum of the world.
1986		J. Ellroy Suicide Hill 139: ‘If I don't hear from you [I] snitch you off [...] as the kingpin motherfucking gun dealer of L.A. County’.
1990		M. McAlary Crack War (1991) 121: A big dealer who [...] goes by the name of Pappy (kingpin drug dealer in area).