Despite being legally blind in his later years due to glaucoma, Kellogg remained actively involved in his foundation and business endeavors until his retirement.

In 1930, he established the W.K. Kellogg Foundation with a focus on improving health, education, and child welfare. Over his lifetime, he donated approximately $66 million to the foundation.

Kellogg was a gifted marketer who used innovative advertising techniques to promote his cereals. For example, he launched a campaign in 1907 where women who winked at their grocers on Wednesdays received free boxes of cornflakes.

Later in life, Kellogg developed a passion for Arabian horses and established the Kellogg Arabian Ranch in California.

W.K. Kellogg co-invented flaked cereal with his brother, John Harvey Kellogg, in 1894 while working at the Battle Creek Sanitarium. However, he later improved the recipe by adding sugar and founded the Battle Creek Toasted Corn Flake Company in 1906, which became the Kellogg Company.

W.K.'s relationship with his older brother, John Harvey Kellogg, was strained. John treated him poorly, assigning menial tasks like shining shoes and shaving him daily. Their business disagreements over the commercial potential of cereal led W.K. to break away and start his own company

Barnum tested the strength of the Brooklyn Bridge using his circus animals.

He entered the circus business later in life.

He played a pivotal role in popularizing opera in the United States

He served as the mayor of Bridgeport.

P.T. Barnum started his entrepreneurial journey at the age of 12 by selling snacks and homemade cherry rum during local gatherings.