Green’s Dictionary of Slang

(US black) a white person; a mixed-race person (see cite 1940).

1932		Eve. Sun (Baltimore) 9 Dec. 31/5: Peck, a white person.
1940		Davis & Dollard Children of Bondage 154: Another Creole [...] is called a ‘nigger’ by the whites and a ‘peck’ by the colored.
1946		Mezzrow & Wolfe Really the Blues 207: Let any of our boys get in a scrape with the pecks down in Memphis [...] and the news buzzed back to us on Seventh Avenue quicker than right now.
1957		H. Simmons Corner Boy 104: That’s Trashwagon [...] One of them pecks from down home.
1966		Current Sl. I:2 4/2: Peck, n. A white person.
1971		D. Goines Dopefiend (1991) 28: Make sure that peck don’t die on us.
1980		J.L. Gwaltney Drylongso xvii: peck – a derogatory term for Southern white men. [Ibid.] 61: The only thing a peck cares about is, ‘Can I get away with it?’.