A founding member of the New Haven Paint & Clay Club, John I.H. Downes graduated from Hopkins Grammar School in New Haven and then traveled to Paris to study music and languages. From 1888 to 1892 he attended the Yale School of the Fine Arts, followed by a year at the Art Students League in New York and a year at the Ecole des Beaux Arts in Paris. He received a B.F.A. from Yale in 1898, and in 1900 became Librarian for the Yale School of the Fine Arts, a job he held until his retirement in 1923. He painted landscapes in both oil and watercolor and had several one-man shows. His work is in the Yale University Art Gallery and the National Gallery of Art.

John I.H. Downes was one of the prime movers in the New Haven Paint & Clay Club from the first exhibition in 1900 until his death in 1933. He exhibited in nearly every show, and he was President of the Club from 1910 to 1926. Beginning in 1928, he contributed awards for the best landscape, and his estate continued these awards until 1951. His brother, William Howe Downes, was an art critic and author. His nephew, John Downes Whiting, was a Club member, and his great nephew and namesake John I.H. Bauer was a Director of the Brooklyn Museum.