Green’s Dictionary of Slang

(orig. US) a prison.

1954		Hal Ellson ‘Pretty Boy’ in Tell Them Nothing (1956) 121: Don’t talk or you’ll have us all in the slam.
1965		C. Brown Manchild in the Promised Land (1969) 445: If I go to a slam in Jersey [...] I still run into a lot of cats I know.
1972		E. Sanders Family 58: Hinman bailed Snake and Sandy out of the slams.
1976		N. Thornburg Cutter and Bone (2001) 77: And if I wind up sweating another day in the slam, so what, huh?
1990		J. Wambaugh Golden Orange (1991) 26: Winnie was going to the slam without a doubt.
2001		(con. 1964–8) J. Ellroy Cold Six Thousand 251: Jack’s in the slam. Jack’s pissed off and hungry.