Born in Dumferline, Scotland, James Bonar immigrated to the United States in 1885, settling in Pittsburgh to work as a mechanical engineer for the Carnegie Steel Company. Andrew Carnegie was not only a fellow Scotsman but also hailed from Dumferline, and over time the two became friends and associates with a common interest in the arts- Carnegie as a patron and philanthropist and Bonar as an artist himself.
A self-taught artist, Bonar considered himself "a businessman who pursues arts as a pastime" limiting his painting to his off hours through a succession of engineering and management posts at other companies like Pittsburgh Gage and Supply Company, U.S. Steel Corporation and the Pittsburgh Board of Education. His preferred subjects were industrial scenes and city views, though he is known to have painted pastorals and other subjects.
Throughout Bonar was involved in the Pittsburgh artist community co-founding the One Hundred Friends of Pittsburgh Art, and also serving as president of the Associated Artists of Pittsburgh for over a decade. A frequent exhibitor at the Associated Artists of Pittsburgh's annual shows, his work was also displayed in exhibitions at the Corcoran Galleries in Washington, Philadelphia's Memorial Hall, and the St. Louis Art Museum. During the first World War, a work of Bonar's was selected as artwork for a U.S. Government recruitment poster.
The papers of James Bonar, including correspondence with Carnegie and H.C. Frick, are now part of the collections of the University of Pittsburgh Library.