Clayton Knight was born in Rochester, New York on March 30, 1891 and, between 1910 and 1913 studied art with Robert Henri and George Bellows to become a painter. In 1917, during WW!, he enlisted in the US Army Signal Corps hoping to join the aviation section. To speed up American training some 2,500 future pilots were sent to England and France for advanced pilot training. Clayton Knight was one of the original 150 American pilots sent to England in the summer of 1917. Clayton began his training with No. 44 Squadron of the Royal Flying Corps, newly formed at Hainault Farm, Essex, on 24 July 1917. They were a Home Defence Squadron that pioneered the use of the Sopwith Camel fighter aircraft for night operations and achieved their first victory on 28/29 January 1918. He flew a British de Havilland 9, which Clayton was flying on 5 October 1918, when he was shot down by Oberleutnant Harald Auffahrt the Commanding Officer of Jasta 9. Auffahrt was a top ace that scored 26 kills in WW I and during the shooting down of the de Havilland bomber, Clayton Knight was wounded but survived his crash on German soil. The war ended while Knight was a prisoner of war in a German hospital. Following a full recovery in a British hospital Clayton returned to New York and resumed his aviation art career. Moore went on to exhibit his work at Associated American Artists and collect what might have been the largest archive of airplane art, which he began in 1928. At that time he began to specialize in the illustration of aviation books.

In the 1940s he was living in Greenwich Village in New York when he and Canadian pilot Billy Bishop, with funding from Homer Smith, and assistance from several pro-war German emigres, formed the Clayton Knight Committee, which was a covert and illegal recruitment agency established in 1940 to transport Americans up to Canada to train and fight for the Allies during the period of U.S. neutrality prior to the U.S. declaring war on Germany and Japan. Bishop would spend most of 1940 with Winston Churchill in London, leaving Knight to find new partners to set up an office, including pro-war German emigres. Headquarters were set up in the Waldorf-Astoria Hotel in New York. Later, other branch offices were created in other cities across America, such as Spokane, San Francisco, Los Angeles, Dallas, Kansas City, Cleveland, Atlanta, Memphis, and San Antonio. Committee expenses were met through a revolving bank account. President Roosevelt who secretly assisted the committee's needs and ensured the authorities turned a blind eye and focused on their prime goal of bringing down the German Abwehr spy network which blanketed America at the time. Intelligence and cooperation from the committee, eventually assisted the fall of the German spy rings in Manhattan.

Knight was married to fellow illustrator, artist/designer Katherine Sturges (1890-1979). Their son, Hilary Knight studied at the Arts Students League with Reginald Marsh and is best known for illustrating the "Eloise" books. Clayton Knight died in Danbury, Connecticut, USA in July of 1969.