William L. Kenly was born in Springwood, Baltimore City, Maryland on February 18, 1864. The general was graduated from the U.S. Military Academy in 1889 and served his early years in the Artillery. He was twice awarded the Silver Star for gallantry in action during the war with Spain.

In July of 1917 he went to Europe with the American Expeditionary Forces as commanding officer of the 7th Field Artillery, after a brief tour with Signal Corps and qualification as a pilot in San Diego, California. During World War I, he worked closely with the Royal Flying Corps and became Chief of Air Service for the American Expeditionary Force and then Chief of Staff for General Headquarters, American Expeditionary Force. The general served as head of U.S. military aviation in World War I.

On April 24, 1918, President Wilson chose him as head of the Division of Military Aeronautics, still under the Signal Corps. Brigadier General Kenly was promoted to Major General five days later. The following month the Division of Military Aeronautics became a division independent of the Signal Corps. Kenly served in this assignment until December 1918.

General Kenly retired October 31, 1919, and died January 20, 1928, in Washington D.C.