I believe the U.S developed the first aircraft carrier, the U.S.S LANGLEY right after WW I. But I could be mistaken.
or was it the HMS Argus??
I think the Langley had the credit of seeing the first person to take off from its deck.
HMS Ark Royal was arguably the first modern aircraft carrier. She was originally laid down as a merchant ship, but was converted on the building stocks to be a hybrid airplane/ seaplane carrier. Launched in 1914, she served in the Dardanelles campaign and throughout World War I.
The first strike from a carrier against a land target took place on July 19, 1918. Seven Sopwith Camels launched from HMS Furious attacked the German Zeppelin base at Tondern, with two 50 lb bombs each. Several airships and balloons were destroyed, but as the carrier had no method of recovering the aircraft safely, two of the pilots ditched their aircraft in the sea alongside the carrier while the others headed for neutral Denmark.
The first ship to have a full length flat deck was HMS Argus the conversion of which was completed in September 1918, with the U.S. Navy not following suit until 1920, when the conversion of USS Langley (an experimental ship which did not count against America's carrier tonnage) had completed. The first American fleet carriers would not join the service until 1928 (USS Lexington and Saratoga).