USS Pennsylvania (ACR-4)
The history of the USS PENNSYLVANIA, later renamed the PITTSBURGH (Armored Cruiser 4), begins when her hull was laid down on August 7, 1901 by the William Cramp and Sons Ship Building Company in Philadelphia.  She was launched on August 22, 1903; sponsored by Miss Coral Quay, daughter of Senator Matthew S. Quay; and commissioned on March 9, 1905 at League Island, with Capt. Thomas C. McLean in command.  PENNSYLVANIA would operate primarily on the East Coast and in the Caribbean until September 8, 1906 when she cleared Newport for the Asiatic Station.  From the Asiatic Station, she was ordered to San Francisco on September 27, 1907 for west coast duty.  Shortly after returning from port visits in Chile and Peru, on January 4, 1911, the cruiser PENNSYLVANIA entered Mare Island Shipyard for urgent and unusual "alterations," prosaically described as "erection of platform in connection with aviation meet."
Eugene B. Ely would visit the yard to check on the work, which involved building a wooden platform 133 feet 7 inches long (from the mainmast to just over the fantail) and 31 feet  6 inches wide over the main deck. The deck was angled upward from the stern and over the after turret and secured to the mainmast.  At its after end it was angled down 30 degrees over the stern for a length of 14 feet 3 inches.  Bulwarks of 2-inch wood plankings extended up the sides for about 2 feet to prevent the aircraft from falling into the sea.  Running the length of the platform, parallel guide rails of 2-by-4-inch scantling, placed 12 feet apart, confined the aircraft to the center of the landing deck.  The arresting gear consisted of parallel lines of twenty-two pairs of 50-lb sandbags athwart the deck, each pair connected by a twenty-one thread line, tightly stretched across the guide rails.  To prevent the aircraft from sluing, each bag was accurately weighed.  The bags were placed 3 feet apart and covered 75 feet of the deck.  As a final fail-safe measure, two canvas screens, 20 feet high and 6 feet apart, were fitted just abaft the mainmast.
This single event opened the era of naval aviation.  While in reserve at Puget Sound, between 1 July 1911 and 30 May 1913, the cruiser trained naval militia.  The USS Pennsylvania was later renamed the PITTSBURGH (Armored Cruiser 4) on 27 August 1912 to free the name Pennsylvnia for a new battleship.

Ten years later the Mare Island Naval Shipyard build collier JUPITER would enter the Norfolk Navy Yard to have a flight deck installd, making her a "Covered Wagon" and the Navy's first aircraft carrier LANGLEY.
The workers at the ship yard had never seen anything like it before.  In less than fourteen days, Mare Island had built a steel frame, errected a wooden platform upon it, affixed ropes which were stretched across the platform and anchored to sand bags on both ends, all before the ship shoved off for the San Francisco Bay.

It was there, on the 18th of January, Eugene B. Ely cranked up his Curtiss biplane, wrapped a few inflated inner tubes around himself in case he missed, and kited across the bay toward the PENNSYLVANIA and thus became the first man in the world to land an airplane on a ship.
Eugene B. Ely flies onto the USS Pennsylvania
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By CW4 Mark J. Denger
California Center for Miltiary History
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California Center for Military History