I may be completely off, but I think the first to come up with a chocolate candy bar were Hershey's Company of Hershey Pennsylvania.
Sorry, wrong. While Chocolate was discovered thousands of years ago in South America, it was made into bitter drinks, the Mayans enjoyed drinking the Cocoa drink very much and later it was ported to Spain by the Spaniards.
It wasn't until years later that Cocoa was made into candy, for confectionery purposes. But the first recorded to come up with a wrapped chocolate candy bar was a couple of men from Canada "The first wrapped chocolate bar was sold in 1910 by the Ganong Brothers company in Canada"
Here is the full article on Chocolate and Chocolate bars: