Hartmann, born on the artificial island of Dejima, Nagasaki to German businessman Carl Herman Oskar Hartmann and Japanese mother Osada Hartmann and raised in Germany, arrived in Philadelphia in 1882 and became an American citizen in 1894. An important early participant in modernism, Hartmann was a friend of such diverse figures as Walt Whitman, Stéphane Mallarmé and Ezra Pound.
His poetry, deeply influenced by the Symbolists as well as orientalist literature, includes 1904's Drifting Flowers of the Sea and Other Poems, 1913's My Rubaiyat and 1915's Japanese Rhythms. His works of criticism include Shakespeare in Art (1901) and Japanese Art (1904). During the 1910s, Hartmann let himself be crowned King of the Bohemians by Guido Bruno in New York's Greenwich Village. Hartmann wrote some of the earliest English language haiku.
He was one of the first critics to write about photography, with regular essays in Alfred Stieglitz's Camera Notes. Hartmann published criticism and conducted lecture tours under the pseudonym "Sidney Allen."
Later years found him living in Hollywood and, by 1942, on his daughter's ranch outside Banning, California. Due to his age and health conditions, Hartmann was one of only a few Japanese Americans on the West Coast to avoid the mass incarceration during World War II, although the FBI and local officials visited the ranch often to conduct investigations. In 1944, he died while visiting another daughter in St. Petersburg, Florida. A collection of his papers is held at the University of California, Riverside, including correspondence related to his obtaining permission to remain in Banning during the war.
- Christ: A Dramatic Poem in Three Acts (play, 1893)
- Buddha: A Drama in Twelve Scenes (play, 1897)
- Mohammed (play, 1899)
- Schopenhauer in the Air: Seven Stories (1899)
- Shakespeare in Art (1900)
- A History of American Art (1901)
- Japanese Art (1903) 
- Drifting Flowers of the Sea and Other Poems (1904) 
- Landscape and Figure Composition (1910) 
- My Theory of Soul Atoms (1910) 
- The Whistler Book (1910) 
- My Rubaiyat (1913) 
- Permanent Peace: Is it a Dream? (1915)
- Tanka and Haikai: Japanese Rhythms (1916) 
- The Last Thirty Days of Christ (1920) 
- Confucius: A Drama in Two Acts (play, 1923)
- Moses: A Drama in Six Episodes (play, 1934)
- Buddha, Confucius, Christ: Three Prophetic Plays (reprint collection, 1971)
- Niiya, Brian. "Sadakichi Hartmann". Densho. Retrieved 12 August 2014.
- William Bryk (26 January 2005). "King of the Bohemians". The New York Sun.
- Weaver, Jane Calhoun (ed.) (1991). Sadakichi Hartmann: Critical modernist: Collected Art Writings. Berkeley: University of California Press. p. 10. ISBN 0520067673.
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