Cracker Jack is an American brand of consisting of molasses-flavored, caramel-coated popcorn and peanuts. Since at least March 1896, Cracker Jack has advertised, “The More You Eat, the More You Want.”
 
However, that slogan was not original with Cracker Jack, and had applied to both peanuts and popcorn earlier than 1896. “Why them Pea Nuts at Jos Laughlins, I’ll not buy any more. Cause, why, the more you eat the more you want and I don’t want to be eatin’ all the time” was printed in The Star of the Valley (Newville, PA) on July 2, 1869. “Well, the more you eat the more you want” (peanut brittle—ed.) was printed in the Middletown (NY) Daily Press on February 6, 1893. “W. J. Du Paw does a thriving business selling hot pop corn. The more you eat the more you want” was printed in the Burlington (VT) Clipper on October 13, 1893. “It is said by those who have tasted it that Congressional pie is very toothsome, and, as with peanuts, the more you eat the more you want” was printed in the Morning Call (Allentown, PA) on June 25, 1895.
 
Other foods that have used the “the more you eat, the more you want” slogan include halibut (1875), burgoo (1877), bananas (1885), cream chocolates (1888), meat (1890), peanut taffy (1893) and ice cream (1893).
 
 
Wikipedia: Cracker Jack
Cracker Jack is an American brand of snack food consisting of molasses-flavored, caramel-coated popcorn and peanuts, well known for being packaged with a prize of trivial value inside. The Cracker Jack name and slogan, “The More You Eat The More You Want”, were registered in 1896. Some food historians consider it the first junk food.
   
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24 July 1869, The Star of the Valley (Newville, PA), pg. 3, col. 1:
“WELL I WON’T.”—“Wont what, Jim? What’s the matter—what’s up?” “Why them Pea Nuts at Jos Laughlins, I’ll not buy any more. Cause, why, the more you eat the more you want and I don’t want to be eatin’ all the time.”
 
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21 May 1875, Boston (MA) Daily Globe, pg. 3, col. 3:
A Wise Remark and Adjournment. 
(...)
“Yes,” said he, “knowledge is a good thing; it is a great thing; it’s like baked halibut—the more you eat the more you want.”
 
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15 May 1877, Cincinnati (OH) Enquirer, “Lexington Letter,” pg. 2, col. 2:
The appetite for it (burgoo—ed.) increases with the supply, and the more you eat the more you want, and you can’t quit devouring it until you are full up to the chin.
 
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8 September 1877, The Shenango Valley Argus (Greenville, PA), “Old Cook Again,” pg. 8, col. 2:
It’s like “Old Cook’s” description of drinking lager beer and eating pretzels—“The more you eats the more you wants to drink, and the more you drinks the more you wants to eat.”
     
18 June 1885, The Maine Farmer (Augusta, ME), “The Banana Trade,” pg. 4, col. 3:
With many, the love of bananas is not a natural, but rather an acquired taste; but as a rule, the more you eat of them the more you want.
 
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18 December 1888, Pittsburg (PA) Press, pg. 8, col. 2 ad:
JUST MELT IN YOUR MOUTH.
The More You Eat the More You Want of Rockwood & Co.‘s Cream Chocolates.
 
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1 November 1890, The Daily Democrat (Huntington, IN), “Local Nuggets,” pg. 3, col. 1:
A happy thought, the more you eat the more you want of the fresh meats at Shearer’s meat market. Prices a-way down.
 
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6 February 1893, Middletown (NY) Daily Press, pg. 2, col. 7 ad:
Peanut : Brittle!
Good!
Well, the more you eat the more you want
(H. H. Maydole’s.—ed.)
 
11 February 1893, Trenton (NJ) Times, pg. 1, col. 2 ad:
Try New England Peanut Taffy; it is pure in every sense of the word, tender as lettuce, and does not stick between your teeth a bit; appetizing in the extreme, and the more you eat the more you want to eat. These are the expressions of every one who has tried it. Camera’s Confectionery, sole agent in Trenton. Beware of imitations.
 
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17 July 1893, Evening Gazette (Cedar Rapids, IA), pg. 6, col. 6 ad:
Ice Cream, the Great Cooler of the Day.
The more you eat the more you want, when
COFFITS MAKES IT.
 
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13 October 1893, Burlington (VT) Clipper, “Winooski News,” pg. 5, col. 2:
W. J. Du Paw does a thriving business selling hot pop corn. The more you eat the more you want.
 
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2 May 1895, Morning Tribune (Altoona, PA), pg. 5, col. 3 ad:
Velvet Taffy.
Do you know what that is? Try it and find out. In 10, 15 and 25c packages. The more you eat the more you want, at
McMURTRY & AKERS’S
 
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25 June 1895, Morning Call (Allentown, PA), “Congressional Pie,” pg. 1, col. 1:
It is said by those who have tasted it that Congressional pie is very toothsome, and, as with peanuts, the more you eat the more you want.
   
5 March 1896, The Northwestern (Northwestern University, Evanston, IL), pg. 10, col. 1 ad:
CRACKER JACK
The more you eat the more you want, a great big bag full for 10 cents, smaller bag, 5 cents.
(H. E. Chandler & Co.—ed.)
 
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17 March 1896, Logansport (IN) Journal, pg. 22, col. 6:
The more you eat the more you want of Foley’s Cracker Jack.
 
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27 April 1896, Davenport (IA) Daily Times, pg. 3, col. 4 ad:
Cracker Jack.
Put up in five cent packages, perfectly adaptable for hot weather, very nutritious, toothsome and gifted with health giving properties. The more you eat, the more you want. Try it, you can carry it right in your pocket. To be found at Charley’s fruit stand.
 
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2 June 1896, The Daily Times (New Brunswick, NJ), pg. 8, col. 5 ad:
Cracker Jack
A NEW CONFECTION. The more you eat, the more you want. Try it.
(McCurdy & Gillette.—ed.)