| Nude, Man | | 1927 | | | First Prize |
| Nude, No. 3 | | 1929 | | | Honorable Mention |
| Nuns at St. Augustine's Covent, Lakewood | | 1923 | | | |
| Nut Spoon | | 1931 | | | |
| Nut Spoon | | 1937 | | | |
| Nymphaca | | 1938 | | | |
| O Tempora! O Mores!, or "No Cigarette" | | 1938 | | | Third Prize |
| Obiit | | 1939 | | | |
| Oblivion | | 1935 | | | |
| October 8th, Piccola Marina | | 1932 | | | |
| October Afternoon | | 1919 | | | |
| October Haze | | 1919 | | | |
| October Pallor | | 1935 | | | |
| October Still Life | | 1938 | | | |
| October, Pownal, Vermont | | 1923 | | | |
| October, Rockefeller Park, Cleveland | | 1923 | | | |
| October's Shadows | | 1937 | | | |
| O'Donnell Abu | | 1931 | | | Third Prize |
| Of a Series | | 1936 | | | |
| Of Another Time | | 1925 | | | |
| Of Other Days | | 1931 | | | |
| Off Coltman Road | | 1931 | | | |
| Off Santiago, Cuba | | 1923 | | | |
| Oh! Doggie | | 1929 | | | |
| Oh! Oh! | | 1939 | | | Honorable Mention |
| Ohio | | 1937 | | | |
| Ohio Canal | | 1939 | | | Third Prize |
| Ohio Canal | | 1927 | | | |
| Ohio Farm | | 1931 | | | |
| Ohio Fields | | 1928 | | | |
| Ohio Landscape | | 1936 | | | Second Prize |
| Ohio Landscape | | 1937 | | | |
| Ohio Landscape | | 1931 | | | Honorable Mention |
| Ohio River | | 1936 | | | |
| Ohio to West Virginia | | 1925 | | | |
| Oil | | 1929 | | | |
| Oil Composition | | 1938 | | | Second Prize |
| Oil Foam | | 1933 | | | |
| Ol' Peckerwood | | 1939 | | | |
| Old Actor | | 1939 | | | First Prize |
| Old Age | | 1931 | | | |
| Old and New | | 1929 | | | |
| Old Barn | | 1932 | | | |
| Old Bill Townsend | | 1929 | | | Second Prize |
| Old Boat on the Seine | | 1919 | | | |
| Old Building | | 1930 | | | |
| Old Canal House, South Newburg, Ohio | | 1919 | | | |
| Old Church | | 1936 | | | |
| Old Church, Richmond | | 1931 | | | |
| Old Doorway | | 1932 | | | |
