Morton was the son of Major-General Jacob Morton, an honorary member of the National Academy of Design. Born and raised in New York City, he had begun to work as an artist by 1815 when his view on the Susquehanna was reproduced in the Port Folio. Although Morton was not a founding member of the National Academy, he was immediately elected to serve as its secretary. He enrolled in the Academy's antique school during its first year, and in 1827 he exhibited Constance, a portrait of the heroine from Sir Walter Scott's poem Marmion. He continued to serve as the Academy's secretary until 1844 and during these years he exhibited both historical paintings and landscapes in its annual exhibitions. After resigning as secretary, Morton began exhibiting his works at the American Art Union. Although he continued to reside in New York for his remaining life, Morton produced few paintings after 1850.
Like Whitehorne himself, John L. Morton was not required to submit a portrait of himself when he was elected an associate in 1827. It was, consequently, probably executed shortly after the by-law requiring portraits was adopted in 1838.
