The first modern commercial breakfast cereals were created by the American Seventh-day Adventists. The Adventists formed the Western Health Reform Institute in the 1860s. The Institute was later renamed the Battle Creek Sanitarium after its location in Battle Creek, Michigan. The Adventists manufactured, promoted, and sold whole-grain cereals.

Doctor John Harvey Kellogg, the superintendent of The Battle Creek Sanitarium in Michigan and an Adventist, was trying to improve the diet of hospital patients. (He also believed that spicy and sweet foods increased passions, and passion, sex, and especially masturbation were all bad things that had to be "cured.") He was searching for a digestible bread substitute using the process of boiling wheat. Kellogg accidentally left a pot of boiled wheat to stand and the wheat became tempered (softened). When Kellogg rolled the tempered or softened wheat and let it dry, each grain of wheat emerged as a large thin flake. The flakes turned out to be a tasty cereal. On May 31, 1884, John Harvey Kellogg filed for patent for "flaked cereals and process of preparing same."Â Patent #558,393 was issued on April 14, 1896.

Dr. Harvey's brother, Will Keith (W.K.) Kellogg, kept experimenting until he flaked corn in 1898, and invented corn flakes.

The Kellogs formed the Sanitas Food Company. At first, they sold their products mainly by mail order to their ex-patients, but then began advertising in newspapers and on billboards.

W.K. Kellogg founded the Battle Creek Toasted Corn Flake Company in 1906. He added sugar to the flakes to make them more palatable to a mass audience, a move that his brother did not approve. W.K. Kellogg spent heavily on advertising, including a campaign telling consumers to "wink at your grocer and see what you get." What they got was a free sample of W.K.'s corn flakes. The campaign increased sales by a factor of fifteen in New York City. In 1909, W.K. added a special offer, the Funny Jungleland Moving Pictures Booklet, to anyone who bought two boxes of the cereal. This same premium was offered for 22 years.

A former patient of the Battle Creek Sanitarium named C. W. Post started a rival company, as well as the major other brand of corn flakes in the United States, called Post Toasties. Many other brands of corn flakes were produced by various manufacturers. More than 40 cereal companies opened in the United States in the early 20th century.

The Kellogg brothers fought over the Kellogg name, which they both used. In 1911, W.K. succeeded in a lawsuit to gain exclusive use of the Kellogg name in the United States. In 1914, corn flakes were introduced to Canada, and W.K.'s exclusive use of the Kellogg name extended to international markets after a legal battle that lasted from 1916-21. W.K.'s company was the Kellogg Cereal Company from 1922.

Kellogg family friend Nansi Richards, a harpist from Wales, suggested that the mascot for Kellogg's corn flakes should be a rooster or cockerel. The Welsh word for cockerel is ceiliog (pronounced "kelog"). Kellogg's introduced a green cockerel named Cornelius (Corny) Rooster as the long-time mascot of corn flakes.