Original: The Department of the Navy of the United States of America ( DON ) was established by an Act of Congress on 30 April 1798 , to provide a government organizational structure to the United States Navy and , from 1834 onwards , for the United States Marine Corps , and when directed by the President , of the United States Coast Guard as a service within the Navy .
Simplified: The United States Department of the Navy was created by the United States Congress on April 30 , 1798 . It was created in order to give civilian leadership and administration to the United States Navy and the United States Marine Corps .