Contrary to the article Souhern Irelands existence as a political entity did not end on  December  Northern Ireland and Southern Ireland became autonomous regions of the newly created Irish Free State on  December  under terms of the Irish Free State Constitution Act  I cannot find evidence that Southern Ireland ever ended I speculate that the term Southern Ireland may not have been used because the Free State and the Republic of Ireland claimed sovereignty over the whole island in their constitutions I would be greatful if someone can shed light on this