The son of an English farmer, Benoni Irwin developed an interest in art during his youth. Despite parental objections, he moved to Toronto in 1860 or 1861, where he attended the School of Practical Science, spending his spare time copying the oil reproductions, prints, and plaster casts in the collection of the educational museum at the Toronto Normal School. Several years later, he was in New York as a student in the National Academy Antique (1864-6) and Life (1865-7) Schools. One of his school projects, a chalk study of wrestlers, was exhibited in the 1866 Annual, an unusual honor for a student.
The Toronto city directories list Irwin as a portrait painter for 1868 and 1869, and he contributed regularly to the Upper Canada Provincial Exhibitions between 1861 and 1868. His time back in Canada must have been short, however, for he was soon studying in Rome and under Emile August Carolus-Duran in Paris. After several years in Europe, he returned to spend much of the 1870s in the San Francisco area. Although his final base of operations was New York City, he appears to have executed portraits in Chicago, Baltimore, and Louisville, KY (the home of his brother), as well.
Irwin had a summer home near Lake Waumgumbaug, Connecticut. He drowned in that body of water when he caused a small boat to capsize after he stood up in it to sketch.
