Historic county of Ireland
Down
An Dún / County of Down
Province: Ulster
Strangford Lough within, Mournes above, Irish Sea beyond.
Down is one of Ireland’s most maritime counties. The long Ards Peninsula encloses Strangford Lough from the open Irish Sea; Belfast Lough frames the north; and Carlingford Lough closes the south-western coast.
Between these waters lie rolling lowlands which rise dramatically in the south into the granite Mourne Mountains. Sea penetrates far into the county before the land itself rises abruptly into mountain, giving Down one of Ireland’s strongest combinations of maritime and upland geography.
- Dal Fiatach kingdom
- St. Patrick's Arrival (432 AD)
- Mournes and Strangford Lough
- Area: 950 sq miles / 2,460 sq km
- Population: 528,983
- County Top: Slieve Donard (2,789ft / 850m)
County geography
Current Census
Contemporary Census profile
Northern Ireland Census 2021. Detailed contemporary statistics are available in the Geographic County Census Explorer.
- Population density
- 583.1 people per sq mi (225.14 people per km²)
- Population
- 553,947
Strangford Lough and the Ards
The Ards Peninsula forms a long eastern arm between Strangford Lough and the open sea.
The lough itself is effectively an inland marine landscape, filled with islands, tidal channels, mudflats and sheltered shores. It gives eastern Down a geography quite unlike the open Irish Sea coast only a short distance away.
Where the Mournes meet the sea
Southern Down is dominated by the Mourne Mountains. Granite ridges rise dramatically above the lower coastal country and descend towards the sea.
The closeness of high mountain and coast is one of Down’s most memorable geographical relationships.
The northern urban edge
Northern Down turns towards Belfast Lough and the Lagan, where the county enters a much more densely settled landscape.
Belfast crosses the geographic Antrim–Down boundary, demonstrating particularly clearly how an urban area can spread across older county geography without erasing it.
County questions
Questions about Down
Is Belfast partly in Down?
Yes. Belfast crosses the geographic boundary between Antrim and Down, with the Lagan providing the traditional line through much of the city.
Is Strangford Lough a lake?
No. Despite its name, it is a tidal sea lough connected directly to the Irish Sea.
County record
Names and continuity
- Formal name
- County Down
- Local name
- An Dún
- Province
- Ulster
- Alternative name
- County of Down
- Foundation
- Pre-16th Century
Down, Downshire and County Down are forms associated with the county. Down is one of the nine geographic counties of Ulster, a province which must not be confused with Northern Ireland.