Green’s Dictionary of Slang

(US Und.) a police dragnet, i.e. the systematic searching of a large area, even a whole town or city.

1920		Electrical Experimenter June 151/3: He told me that he was certain that Coates shot at him. We threw out a drag and landed Coates within an hour.
1931		J. Wilstach Under Cover Man 34: Send out a drag for them before they start to work.
1940		J.G. Brandon Gang War 184: The ‘Sooper’s’ put a ‘drag’ out for him.
1949		W.R. Burnett Asphalt Jungle in Four Novels (1984) 245: You mean they got the drag out again.
1969		D. Pendleton Executioner (1973) 112: He had over reacted to Braddock’s decision for Mafia drag.