Green’s Dictionary of Slang

1. a Prohibitionist, dedicated to the cause of eradicating alcohol.

1889		Century Dict. 1784/2: Dry [...] a member of the Prohibition party.
1896		Chicago Record 11 Feb. 6/5: Even though there might be some precincts where the ‘wets’ outnumbered the ‘drys’ — yet the whole country would go dry.
1915		Coconino Sun (Flagstaff, AZ) 9 July 4/2: It is claimed that the ‘wets’ put one over on the ‘drys’ at the christening of the battleship Arizona.
1918		R.H. Knyvett ‘Over There’ with the Australians 75: The only shots these fellows heard all day were the popping of the corks in the wet canteen! (No charge to the ‘drys’ for this story!).
1929		D.H. Clarke In the reign of Rothstein 46: [The author] has had a leading jurist, noted for his stand as a ‘dry,’ serve him liquor in his home.
1931		Ade Old-Time Saloon 3: Nothing will be said or done with the intent of giving offense to the extreme Drys or the extreme Wets or that inbetween population which may be classed as Slightly Moist.
1942		W. Winchell On Broadway 30 Oct. [synd. col.] He’s an honest dry and believes in it. [...] But you can’t care for the company he keeps.
1952		Lait & Mortimer USA Confidential 101: During Prohibition Tobey was politically a dry.
1965		Wodehouse Galahad at Blandings 13: The woman who runs the school is a rabid Dry and won’t let her staff so much as look at a snifter.

2. attrib. use of sense 1.

1932		J. Dixon Free To Love 148: Cathleen glanced down the page. GREENWICH VILLAGE HIT HARD IN DRY RAIDS.
1939		W. Winchell ‘On Broadway’ 8 Nov. [synd. col.] Two low comedy dry agents, Izzy and Moe, were kicking in doors.