Cloud, Minnesota on August 22, 1854, to Henry G. Fillmore, a trader originally from Buffalo, New York, who did business with local Ojibwe, and Mary Georganna Fillmore (née Stone), who was born in New Brunswick, then part of British North America, in modern day Canada.

[1] An ice skating accident when he was ten broke Fillmore's hip and left him with lifelong disabilities.

[2] In his early years, despite little formal education, he studied William Shakespeare, Lord Tennyson, Ralph Waldo Emerson and Charles Lowell as well as works on spiritualism, Eastern religions, and metaphysics.

[3][4] He met his future wife, Mary Caroline "Myrtle" Page, in Denison, Texas in the mid-1870s, while working as a railroad clerk.

The newlyweds moved to Pueblo, Colorado, where Charles established a real estate business with the brother-in-law of Nona L. Brooks, who later founded the Church of Divine Science.

Myrtle subsequently recovered from chronic tuberculosis and attributed her recovery to her use of prayer and other methods learned in Weeks's classes.

In his later years, Fillmore felt so young that he thought that he might be physically immortal, as well as believing that he might be the reincarnation of Paul the Apostle.

[10] Charles later became a convert through his wife's influence and made his first public statement about vegetarianism in an article titled "As to Meat Eating", in 1903.

[10] Charles and his wife operated Unity Inn, a vegetarian restaurant on Tracy Avenue in Kansas City, Missouri.