Department, is a term used, by the U.S. Army, mostly prior to World War I. In 1920, most of the departments were redesignated as corps areas. However, the Hawaiian, Panama Canal, and Philippine Departments retained their old names. In 1939, the Puerto Rican Department was created and in May of 1941 the Panama Canal and Puerto Rican Departments were combined as the Caribbean Defense Command, although each was still referred to as a department.

United States Army