2010 marks the 400th anniversary of the commencement of the plantation of Ulster. This book is a short study of how the plantation impacted on the Gaelic Irish lordship of Tir Chonaill, transforming it within the century after the year 1610, from a powerful autonomous lordship, with a warlike population, into a quiet and well-settled territory, albeit with a still largely unplanted and Gaelic western seaboard in 1710. The settlers in the county were led by the Lowland Scots, mostly from Ayrshire, headed by two powerful Scottish favorites of King James I and VI himself. This study analyzes how the Donegal plantation grew and consolidated itself throughout the 17th-century, helped in large measure by the manner in which the Gaelic Irish population of Donegal became isolated in the west of the county, where it had a development which was almost separate and distinct from the Gaelic Irish in the rest of the province. The importance of the exiled Gaelic nobility of Tir Chonaill, in Spain, Rome, and Spanish Flanders throughout the 17th-century, is also discussed.