Born and raised in Dublin, Ireland, he has written on aspects of the historical geography of rural Irish communities in the nineteenth and twentieth centuries and on the history of Irish immigrant communities in Canada and the United States. William teaches courses on Historical Geography, Urban Historical Geography, and North American Immigration, among others. His 2013 book, Between Raid and Rebellion: the Irish in Buffalo and Toronto 1867-1916 (McGill-Queen’s University Press) received awards from the American Committee for Irish Studies, the Canadian Historical Association, the Geographical Society of Ireland, and the Ontario Historical Society.