Fenn was born at Richmond, near London, England in 1837.
Fenn started as a wood engraver, serving and apprenticeship with the firm, Dalziel of London.
He soon turned to drawing for illustration and watercolor painting.
In 1857 he made a trip to the U.S. to see the Niagara Falls and settled in New York where he worked first as a wood engraver.
In 1862 he married Marian Thompson of Brooklyn.
After an extended wedding trip to England and Italy, where Fenn studied painting, his focused on illustration in New York.

He settled in Montclair, New Jersey, around 1865.
His first highly successful commission was to illustrate Whittier's Snow-Bound published by Boston's Ticknor and Fields in 1867 for the Christmas trade (dated 1868).
Its tiny images apparently opened the eyes of many to the artistic possibilities of wood engravings, and it is often referred to as the "first gift book published in America," although it had predecessors.
Fenn is best known for the engravings he contributed with his friend Douglas Woodward to three massive books filled with wood and steel engravings that were published by New York's D. Appleton and Co.: Picturesque America (1872–74), edited by William Cullen Bryant, which started as a serial in Appleton's Journal in 1870; Picturesque Europe (1875–79),  and Picturesque Palestine, Sinai and Egypt (1881–84).
 Other artists contributed to each of these books, but Fenn was the most prolific contributor, and his innovative page designs combining image and text popularized this approach.
Fenn and his family lived in England from 1873 to 1881 while Fenn worked on Picturesque Europe and Picturesque Palestine.

After returning to the U.S. in 1881, Fenn was a sought-after illustrator for the leading illustrator periodicals, Century Magazine, "Harper's Monthly," "Harper's Weekly," and Scribner's.
 He was commissioned to illustrate landscape throughout the world and the U.S. as well as to produce depictions of architecture and plant life.
As the technologies for printing illustrations changed, Fenn adapted, producing ink drawings for reproduction as process line cuts and later watercolors for reproduction as halftones.
 He also contributed to numerous books of poetry.
An edition of Gray's Elegy in a Country Churchyard published by Roberts Brothers in 1884 was stamped "Harry Fenn Edition" on the front cover.
He was also the sole illustrator of an edition of Tennyson's "In Memoriam", published by Fords, Howard and Hulbert in 1897, in a very different style from his earlier designs for poetry.

Throughout his career Fenn prepared watercolors for exhibition and sale.
He was among the founding members of the American Watercolor Society, attending the second meeting in 1867, and he regularly participated in their exhibitions.
He was a member of the New York Watercolor Club, the Society of Illustrators, and the Salmagundi Club.
He exhibited at the National Academy of Design in 1864 and at the Brooklyn Art Association between 1864 and 1885.
He exhibited at the Centennial Exposition in Philadelphia in 1876 and at the Columbian Exposition in Chicago in 1893, where he was awarded a medal.
Fenn died on April 22, 1911, at his home in Montclair, where he had lived since 1881.
Fenn was born at Richmond, near London, England in 1837. Fenn started as a wood engraver, serving and apprenticeship with the firm, Dalziel of London. He soon turned to drawing for illustration and watercolor painting. In 1857 he made a trip to the U.S. to see the Niagara Falls and settled in New York where he worked first as a wood engraver. In 1862 he married Marian Thompson of Brooklyn. After an extended wedding trip to England and Italy, where Fenn studied painting, his focused on illustration in New York.
He settled in Montclair, New Jersey, around 1865. His first highly successful commission was to illustrate Whittier's Snow-Bound published by Boston's Ticknor and Fields in 1867 for the Christmas trade (dated 1868). Its tiny images apparently opened the eyes of many to the artistic possibilities of wood engravings, and it is often referred to as the "first gift book published in America," although it had predecessors. Fenn is best known for the engravings he contributed with his friend Douglas Woodward to three massive books filled with wood and steel engravings that were published by New York's D. Appleton and Co.: Picturesque America (1872–74), edited by William Cullen Bryant, which started as a serial in Appleton's Journal in 1870; Picturesque Europe (1875–79),  and Picturesque Palestine, Sinai and Egypt (1881–84).  Other artists contributed to each of these books, but Fenn was the most prolific contributor, and his innovative page designs combining image and text popularized this approach. Fenn and his family lived in England from 1873 to 1881 while Fenn worked on Picturesque Europe and Picturesque Palestine.
After returning to the U.S. in 1881, Fenn was a sought-after illustrator for the leading illustrator periodicals, Century Magazine, "Harper's Monthly," "Harper's Weekly," and Scribner's.  He was commissioned to illustrate landscape throughout the world and the U.S. as well as to produce depictions of architecture and plant life. As the technologies for printing illustrations changed, Fenn adapted, producing ink drawings for reproduction as process line cuts and later watercolors for reproduction as halftones.  He also contributed to numerous books of poetry. An edition of Gray's Elegy in a Country Churchyard published by Roberts Brothers in 1884 was stamped "Harry Fenn Edition" on the front cover. He was also the sole illustrator of an edition of Tennyson's "In Memoriam", published by Fords, Howard and Hulbert in 1897, in a very different style from his earlier designs for poetry.
Throughout his career Fenn prepared watercolors for exhibition and sale. He was among the founding members of the American Watercolor Society, attending the second meeting in 1867, and he regularly participated in their exhibitions. He was a member of the New York Watercolor Club, the Society of Illustrators, and the Salmagundi Club. He exhibited at the National Academy of Design in 1864 and at the Brooklyn Art Association between 1864 and 1885. He exhibited at the Centennial Exposition in Philadelphia in 1876 and at the Columbian Exposition in Chicago in 1893, where he was awarded a medal. Fenn died on April 22, 1911, at his home in Montclair, where he had lived since 1881.
Harry Fenn