Harman taught subscription school courses and attended Arcadia College.
He was prosecuted under the Comstock Law for content published in his anarchist periodical Lucifer the Lightbearer. He was arrested and jailed multiple times for publishing allegedly obscene material. Their family later moved to Crawford County, Missouri.
After completing his schoolwork, Harman worked as a Methodist circuit rider and teacher.
Harman married Susan Scheuck in 1866. Although they had several children, only two survived and Susan died in childbirth in 1877.
Harman began his involvement with eugenics and social reform following Susan"s death. In 1879, Harman edited the Kansas Liberal newspaper in Valley Falls, Kansas.
Harman has been credited as one of the founders of what became the eugenics movement.
"He gave the spur and start to this effort. Through his journals, Lucifer, the Light Bearer, later renamed to The Eugenic Magazine, encouraged by a small circle of earnest men and women, he dug down below the surface endeavoring to bring forth a stronger and better type of men". In 1881, Harman co-edited the Valley Falls Liberal, and eventually became the editors
On August 24, 1883, Harman changed the name of the publication to Lucifer, the Light Bearer.
He moved the location of the newspaper several times for financial and philosophical reasons: to Topeka, Kansas in 1890, to Chicago in 1896, and to Los Angeles in 1908. The name of the paper also changed to The American Journal of Eugenics in 1906.
Through his work, Harman rejected all forms of religion and government, including marriage, and promoted freedom, love, wisdom, and the use of knowledge. Due to the radical nature of his views and publication, Harman constantly dealt with lawsuits, charges of immorality, ridicule, and issues with mailing what was considered obscene material through the United States Postal Service.
Consequently, Harman was sentenced and released by courts several times in the 1890s.
He died on January 30, 1910, aged 79, in Los Los Angeles