USS Canonicus ( ID - 1696 ) The second USS " Canonicus " was the Southern Pacific freighter " El Cid " temporarily converted for planting the World War I North Sea Mine Barrage . Newport News Shipbuilding and Dry Dock Company launched " El Cid " at Newport News , Virginia on 7 October 1899 for service between New York City and Gulf of Mexico seaports of New Orleans and Galveston , Texas . The United States Shipping Board took control of the ship from Southern Pacific Steamship Company in 1917 . She was fitted out for United States Navy service by Morse Dry Dock and Repair Company at Brooklyn , New York . Work began on 22 November 1917 . Gun platforms were added for two anti - aircraft guns forward and a 5 " / 51 caliber gun aft . The minelaying conversion enabled her to carry mines on three decks , and included six Otis elevators individually capable of transferring two mines every 20 seconds from the storage decks to the launching deck . Stern ports were cut for launching the mines and the rudder quadrant was raised to give adequate clearance . Watertight subdivision was improved by strengthening existing bulkheads and building two new bulkheads to divide the largest compartments so the ship might stay afloat if only one compartment were flooded . Quarters were enlarged to accommodate messing and berthing arrangements for a crew of about 400 . 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 . Existing coal bunkers on the third deck were replaced with a bunker in the hold forward of the boiler room with chutes to load coal over the mines . Larger boats and heavier anchors required larger davits and anchor windlass , and the mines required specialized handling machinery . USS " Canonicus " was commissioned on 2 March 1918 with Commander Thomas L . Johnson , USN , in command . " Canonicus " cleared Newport , Rhode Island on 12 May 1918 and reached Inverness , Scotland on 27 May 1918 . While operating as part of Mine Squadron 1 from 7 June until the close of the war on 11 November 1918 , " Canonicus " : " Canonicus " returned to Hampton Roads , Virginia , on 3 January 1919 and was assigned to the Cruiser and Transport Force on 7 February 1919 . She made three voyages as a troop transport between the United States East Coast and France , returning 4 , 166 troops to the United States . " Canonicus " was decommissioned on 7 August 1919 and returned to the Southern Pacific Steamship Company . Big Four . In the words of British Rear Admiral Lewis Clinton - Baker , the North Sea mine barrage was the " biggest mine planting stunt in the world ' s history . " The United States converted eight civilian steamships as minelayers for the 100 , 000 mines manufactured for the barrage . The largest of these were four freighters owned by Southern Pacific Steamship Company . Southern Pacific Transportation Company had evolved from the First Transcontinental Railroad to become the dominant transportation provider in California . Owners of the original Central Pacific Railroad were known as the Big Four . Sailors similarly referred to these former Southern Pacific ships as the Big Four .