With the help of his brother John, Will Kellogg promoted cereals, especially corn flakes (maize), as a healthy breakfast food. They started the Sanitas Food Company around 1897, focusing on the production of their whole-grain cereals. At the time, the standard breakfast for the well-off was eggs and meat, while the poor ate porridge, farina, gruel and other boiled grains. The brothers eventually argued over the addition of sugar to their product. In 1906, Will founded the Battle Creek Toasted Corn Flake Company, which later became the Kellogg Company.

Kellogg had a longtime interest in Arabian horses. In 1925, he purchased 377 acres (153 hectares) for $250,000 in Pomona, California, to establish an Arabian horse ranch. Starting with breeding stock descended from the imports of Homer Davenport and W.R. Brown, Kellogg then looked to England, where he purchased a significant number of horses from the Crabbet Arabian Stud, making multiple importations during the 1920s. The Kellogg ranch became well known in southern California not only for its horse breeding program but also for its entertaining, weekly horse exhibitions, open to the public and frequently visited by assorted Hollywood celebrities. Among many other connections to Hollywood, the actor Rudolph Valentino borrowed the Kellogg stallion “Jadaan” for his 1926 movie Son of the Sheik, along with a Kellogg employee, Carl Raswan, who rode in certain scenes as Valentino’s stunt double.

In 1930, he established the W. K. Kellogg Foundation, ultimately donating $66 million to it. His company was one of the first to put nutrition labels on foods. He also offered the first inside-the-box prize for children. Kellogg said, “I will invest my money in people.”

In 1932, Kellogg donated the ranch, which had grown to 750 acres (304 hectares), to the University of California. In 1933, the ranch obtained some of the horses sold in the dispersal of Brown’s Maynesboro stud. During World War II, the ranch was taken over by the U.S. War Department and was known as the Pomona Quartermaster Depot (Remount).

In 1948, the ranch was transferred to the U.S. Department of Agriculture; and in 1949, the land was deeded to the W. K. Kellogg Foundation. Later in 1949, title to the then 813-acre (329-hectare) ranch and horses was passed to the State of California, with the provision that the herd of Arabian horses must be maintained. The ranch became part of the Voorhis unit of what was then known as the California Polytechnic State College in San Luis Obispo. This became known as the Kellogg Campus, and in 1966, it was separated to form California State Polytechnic College, Kellogg-Voorhis.

Will Keith Kellogg died at the age of 91 in Battle Creek, Michigan, on October 6, 1951, of heart failure.