In 1898, Dr. John Harvey Kellogg (sounds familiar?) and his brother Will Keith Kellogg accidentally left cooked wheat out long enough that it became stale. Hoping to turn the stale wheat into long sheets of dough, the Kellogg brothers forced it through rollers, but the rollers flaked the wheat instead. The brothers then toasted the flakes and found it perfectly edible. Later, Will Keith tried the same method on corn and thus was the beginning of corn flakes cereal.
In 1906, W.K. Kellogg created the first consumer batch of Kellogg's Corn Flakes. More than a century later, the Kellogg brothers' cereal empire includes more than 30 products. As of 2013, corn flakes' sugar-coated alternative Frosted Flakes ranked #2 on the list of 10 best-selling cereals in the U.S.
Info from Grandparent.com