When looking up Donegal in "A Topographical Dictionary of Ireland" c.1836, it mentioned that excellent slate was raised near Letterkenny.I seem to recall there may have been wills for Adairs of Letterkenny, but I may have it confused with Litter. Letterkenny is described as being in the Parish of Conwall, bar. of Kilmacrenan, co. Donegal, prov. Ulster, 13 miles west from Lifford, on the road from Lifford to Ramelton and Dunfanaghy. Near this place were the ancient English settlements of Drummore and Lurgagh. At Pynnar's survey in 1619, Mr. John Cunningham had a strong bawn.