Which Commandant served the longest term before Archibald Henderson?

The answer indicating that there was no previous record is valid because Archibald Henderson, known as the "Grand Old Man of the Marine Corps," served as the Commandant for an exceptionally long tenure, from 1820 to 1859. Before Henderson, while there were earlier Commandants like Samuel Nicholas and Robert Mullen, their terms were notably shorter and not continuous. Therefore, the significant duration of Henderson's service made any prior record of a longer-serving Commandant effectively nonexistent, underscoring the historical context of his leadership in the Marine Corps.