There are two versions of the Oh Henry! bar origin story. The manufacturer Nestlé says that the bar was introduced by George Williamson and his Williamson Candy Company of Chicago in 1920. The most popular alternate story is that Thomas Henry, manager of the Peerless Candy Co. in Arkansas City, Kansas, invented a bar he called the "Tom Henry Bar" in the late 1910s, and sold the recipe to George Williamson in 1920. There is no credible documentation of this story, however. 
There are also alternate accounts of the origin of the name of the bar. The story supported by Nestlé is that there was a boy named Henry who frequented George Williamson's second candy shop. He became a favorite of the young girls who worked there, who would say "Oh Henry" when speaking to or about him, and Williamson used this phrase to name his new confection. The other (undocumented) story is that the name was changed from the Tom Henry Bar to Oh Henry! when it was purchased by Williamson. Popular myths are that it was named after O. Henry or Henry Aaron.
The Williamson Company was sold to Warner-Lambert in 1965, which soon sold Oh Henry! to Terson, Inc. Nestlé acquired the United States rights to the brand from Terson in 1984 and continues to produce the confection.
Differences between Nestlé and Hershey versions
In Canada, the bar is currently sold by The Hershey Company and was manufactured at their Smiths Falls, Ontario facilities prior to their closure. Because of Canada's different chocolate standards, the Canadian "Oh Henry!" is not considered a "chocolate bar" and is labeled instead as a "candy bar". The American version labels the bar as "milk chocolate", while the Canadian version contains no milk chocolate at all; it contains a compound chocolate coating. The bars are also different in appearance: the Canadian version is one bar with the fudge in the center, the fudge surrounded with a thin layer of caramel, and the nuts surrounding that layer before it is surrounded in the coating. Hershey sells Oh Henry! bars made in Canada on a very limited basis in the United States as Rally bars, using the trademark of a Hershey product introduced in the 1970s and later discontinued.
In popular culture
- "Oh Henry!". Nestlé. Nestlé. Retrieved 12 November 2018.
- Clayman, Andrew. "Oh Henry! Candy Bar Box by Williamson Candy Co., c. 1950s". MADE IN CHICAGO MUSEUM. Retrieved 12 November 2018. Cite error: Invalid
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- "The Oh Henry!s". CANDYBLOG. Retrieved 16 November 2018.
- "Rally Bar - Candy Blog". Candyblog.net. Retrieved 19 July 2018.
- "From Soup Nazis to Nuts: 100 Best 'Seinfeld' Characters". RollingStone. Rolling Stone, LLC. Retrieved 17 November 2018.
- Harder, Jon. "HardwayHQ Montreal Expos Henry Rodriguez Henry Rodriguez's 1996 in Montreal was Underappreciated". HardwayH2.com. Jon Harder. Retrieved 16 November 2018.