Administration
In 1973 counties ceased to be a unit of administration within Northern Ireland, being replaced by district councils.
Derry City Council, Limavady Borough Council, and Magherafelt District Council all fall within County Londonderry's boundaries. Most of Coleraine Borough Council also covers an area within the county (the remainder being in County Antrim), as well as a part of Cookstown District Council (most of which covers an area in County Tyrone).
Read more about this topic: History Of County Londonderry