While working as an illustrator, William Thorne was enrolled in evening courses at the Chicago Art Institute in the mid 1880s. He had moved to New York by 1887, where he executed portraits to earn a living. Thorne entered the antique class of the National Academy of Design during the 1887-88 term, and won a medal for the first work he exhibitied at the National Academy in 1888.
After deciding to continue his artistic education abroad, Thorne went ot Paris sometime around 1890. He studied at the Academie Julian with Jules Lefevbre and Jean-Paul Laurens, also working with Jean Joseph Benjamin-Constant. During his three years in Paris, Thorne's portrait clients were most often Americans living in France. Before returning to the United States, Thorne painted in Etretat in 1892, and spent time in London.
Thorne settled in New York around 1902, establishing his career as a society portraitist at his Carnegie Hall studio. Among his sitters were the children of Andrew Carnegie and Jay Gould, while John Singer Sargent and William Merritt Chase numbered among his more prominent artist friends. He married Margaret Grace Lowe in 1917.
During the second decade of the 1900s, Thorne returned permanently to Delavan, the city of his birth, building a replica of his Carnegie Hall studio. In this later period in
his career, Thorne was referred to as the dean of Wisconsin portrait painters.
