Leith-Ross emigrated to the United States in 1903, where he first worked for his uncle's coal company. He subsequently took up advertising work in Denver, Colorado.
Leith-Ross exhibited his oil and watercolor paintings at the National Academy of Design and the Pennsylvania Academy of the Fine Arts in the 1910s, and the Art Institute of Chicago in the 1920s. He became a member of the art colony in Woodstock, New York. He won prizes from the Salmagundi Club and the American Watercolor Society.
Leith-Ross authored a book about landscape painting. His artwork is held in private collections, and exhibited at the James A. Michener Art Museum and the Smithsonian American Art Museum.