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
Kellogg Switchboard & Supply Company by the Bell Telephone Trust (which at the time owned most of Kellogg Switchboard's stock), the Illinois Manufacturers' Association, and the Employers' Association of Chicago. Kellogg Switchboard sued to stop the Teamsters from engaging in their sympathy strike, and won an injunction forcing the drivers back to work. The Kellogg company refused to negotiate, fired nearly 90 percent of its workforce, and broke the strike. The company prospered in the early 20th century. It introduced the Relaymatic automatic switching system in 1939 and a crossbar switching system in 1950. The ITT Corporation purchased a controlling interest in the Kellogg Switchboard