Breakfast cereal he launched the Cornflakes brand, which overnight captured a national market. Soon there were forty rival manufacturers in the Battle Creek area. His brother William K. Kellogg (1860–1951) worked for him for many years until, in 1906, he broke away, bought the rights to Cornflakes, and set up the Kellogg Toasted Corn Flake Company. William Kellogg discarded the health food concept, opting for heavy advertising and commercial taste appeal. Later, his signature on every package became the company trademark. The second major innovator in the cereal industry was Charles W. Post, a salesman who was admitted to Kellogg's sanitarium as
Winthrop Kellogg dolphins and sonar. Winthrop Niles Kellogg was born in 1898 in Mount Vernon, New York. He began undergraduate study in 1916 at Cornell University for one year before joining the Great War (World War I) in Europe. For two years he served as part of the American Expeditionary Forces in the US Army Air Service, earning him the prestigious Croix de Guerre. After the war, he returned to undergraduate study at Indiana University. There he met Luella Dorothy Agger of Indianapolis, whom he would marry in 1920. Kellogg and Agger had two children, Donald Agger Kellogg and Shirley Mae Kellogg.