Over the next 37 years, he served in varied positions at sea and ashore, including duty with the Hydrographic Office, the Bureau of Equipment, and the Board of Inspection and Survey. During the Spanish-American War, he commanded the gunboat Eagle in the blockade of Cuban ports; and, in 1905, he returned to the Caribbean to command Yankee and to act as Senior Officer, Naval Forces in Santo Domingo.
Appointed Rear Admiral on 4 May 1910, he served as President of the Board of Inspection and Survey for Shore Stations until becoming Commander, 2d Division, Pacific Fleet in March 1911. A year later, he became Commander in Chief, Pacific Fleet; and, in March 1913, he left the fleet to take up duties on the General Board.
Admiral Southerland retired on 10 July 1914 and died in Washington, D.C., on 30 January 1933.