The Yankee Slip is the wide slipway edging into the water opposite Ely House. It is far wider than would ever be necessary for the launching of any type of boat used in Wexford. During the last few months of the First World War Irish Coastal Waters became inundated with German U-Boats. This began to play havoc with transatlantic shipping. In 1918 to combat this, the British Admiralty began constructing a naval air base at Ferrybank. This would be completed by the US Navy.
The base was part of a four unit establishment: heavy sea guns at Rosslare Harbour; a sonar marine detection base at Kilrane; an airship base at Johnstown Castle and a seaplane base at Ferrybank. Ely House became the officers residence and relations with the people of Wexford were very good. 4 planes arrived up from Queenstown in Sept 1918, and the intention was to build up to 18, but by November there were only 5 available for patrol. The first sub was bombed 3 days after the station became operational in October. There were 4 submarines bombed in total that month, and after that the �Kaisers Tin Cans� became very scarce. In the 8 week period up to the signing of the armistice the planes made 98 patrol flights � 312 hours in the air. These patrols were very effective. The Americans departed after the armistice and the base was abolished; the only thing to remain was the Yankee Slip.