“What has one horn and gives milk?”/“A milk truck.”

A popular milk riddle is:
 
Q: What has one horn and gives milk?
A: A milk truck.
 
The joke has been cited in print since at least 1952.
 
“What has four wheels and flies?”/“A garbage truck” is a similar joke.
 
 
21 September 1952, Leavenworth (KS) Times, “The Junior Times,” pg. 8, col. 5:
What has one horn and gives milk?
Answer: A milk truck.
Gary Stafford, 11,
Easton.
 
26 July 1953, Leavenworth (KS) Times, “The Junior Times,” pg. 14, col. 8:
What has one horn and gives milk?
Answer: A dairy truck.
Mary Ann Emery
911 Delaware.
 
24 October 1957, Bristol (PA) Courier-Times, “Have You Heard These” by Melanie Kupiec, pg. 35, col. 3:
Mary: “What has only one horn and gives milk?”
Sue: ‘‘What?’’
Mary: “A milk truck.”
 
Google News Archive
4 March 1961, Lewiston (ME) Evening Journal, “Try and Stop Me” by Bennett Cerf, pg. 10, col. 6:
What has only one horn and gives milk. A,—A milk truck.
   
Google News Archive
12 June 1964, St. Petersburg (FL) Times, “Fun Time—The Riddle Box,” pg. 12-D, col. 3:
What has one horn and gives milk?
A milk truck.
 
Google News Archive
10 July 1964, Ellensburg (WA) Daily Record, “Fruit Jokes Replace Those of Elephants” by Art Buchwald, pg. 10, col. 7:
“What is white, has one horn, and gives milk?”
 
“A dairy truck.”
 
Google News Archive
11 December 1965, The Free Lance-Star (Fredericksburg, VA), “Fun Time—The Riddle Box,” pg. 4, col. 7:
What is white, has one horn, and gives milk?
A milk truck.
 
Google News Archive
12 November 1968, Deseret News (Salt Lake City, UT), “Funtime Corner—The Riddle Box,” pg. 2B, col. 2:
What is white, has one horn, and gives milk?
A milk truck.
 
Google News Archive
26 June 1978, The Free Lance-Star (Fredericksburg, VA), “Fun Time—The Riddle Box,” pg. 9, col. 2:
What has a horn and gives milk?
A milk truck.
 
Google Groups: eunet.jokes
Not a Unicorn
Ken Johnson
4/20/89
Q: What has one horn and gives milk?
A: A milk lorry.
 
Google Groups: rec.humor
Funky stuff - part 88
Henry Cate IV
10/26/90
Q: What has one horn and gives milk?
A: A milk lorry.
 
Twitter
Adam Lindsay
‏@atl
What has one horn and gives milk?
A milk truck.
Happy christmas, all!
6:24 PM - 25 Dec 2007
 
Google Books
The Mammoth Book of One-Liners
By Geoff Tibballs
London: Constable & Robinson Ltd
2012
Pg. ?:
What has one horn and gives milk?
A milk truck.
 
Humoropedia
102 Funny Laffy Taffy Jokes
BY · PUBLISHED NOVEMBER 27, 2014 · UPDATED NOVEMBER 20, 2015
(...)
72. WHAT HAS ONE HORN AND GIVES MILK? A MILK TRUCK!