The third USS Roanoke was the Southern Pacific freighter El Dia temporarily converted for planting the World War I North Sea Mine Barrage.

She was fitted out for United States Navy service at Tietjen & Lang's shipyard at Hoboken, New Jersey.

Stern ports were cut for launching the mines and the rudder quadrant was raised to give adequate clearance.

The main machinery was overhauled and auxiliary machinery was added for the elevators, for heating the berthing spaces, for refrigerated food storage, for additional fresh water distilling capacity, for magazine sprinklers and galley and washroom plumbing, and enlarged electric generators for lighting and radio communications.

While operating as part of Mine Squadron 1 out of Inverness, Scotland, from 7 June until the close of the war on 11 November 1918, Roanoke:[1] Roanoke then made three trips returning soldiers of the American Expeditionary Forces to the United States before decommissioning and return to Southern Pacific Steamship Company in 1919.