How long did Archibald Henderson serve as Commandant?

Archibald Henderson is notable for serving as the Commandant of the United States Marine Corps for an impressive 38 years, from 1820 until his death in 1859. His lengthy tenure is significant not only because of its duration but also due to the transformative impact he had on the Marine Corps during that time. Henderson implemented various reforms that modernized the organization and expanded its role in military operations, firmly establishing the reputation of the Marines as a formidable fighting force. His leadership during this extensive period was instrumental in shaping the Corps into a more organized and professional military service. This context highlights why 38 years is the correct and historically significant answer.