Aeronautical Division, U.S. Signal Corps
The Aeronautical Division, Signal Corps (1907–1914) was the first heavier-than-air military aviation organization in history and the progenitor of the United States Air Force. A component of the U.S. Army Signal Corps, the Aeronautical Division procured the first powered military aircraft in 1909, created schools to train its aviators, and initiated a rating system for pilot qualifications.
Source: Wikipedia — Aeronautical Division, U.S. Signal Corps (CC BY-SA 4.0)