Brian Mitchell, the best-selling author of "A New Genealogical Atlas of Ireland," has written a book to enable anyone--local people and visitors alike--to research their family history in the city and county of Londonderry (also known as Derry). In the 18th, 19th, and early 20th centuries, the city of Derry was a major port of embarkation for Irish emigrants, and County Derry, in northernmost Ulster, was populated by persons of Gaelic Irish, Gaelic Scottish, Lowland Scottish, and English origins--any number of whom would take part in the exodus to the Americas, Great Britain, and Australasia. "Tracing Derry-Londonderry Roots" recounts Derry's importance in Irish emigration and explains how it impacts genealogical research for the area.