It is obvious that linguistically, as well as politically, Ireland is divided into two broad sections, the north and the south. The former consists of the six counties presently within the state of Northern Ireland and of the large county of Donegal which is part of the Republic of Ireland. The north has a complex linguistic landscape of its own with at least two major historical varieties: Ulster Scots, the speech of those directly derived from the original Lowland Scots settlers, and Mid-Ulster English, the speech of those descendants of English settlers to central parts of Ulster. In addition there is the sociolinguistically complex capital, Belfast. Co. Donegal by and large goes with the rest of Ulster in sharing key features of English in the province and also of the varieties of Irish used there.

The north of the country is quite distinct from the south, accents of northerners being immediately recognizable to southerners. A dividing line can be drawn roughly between Sligo, just south of Co. Donegal, and Dundalk on the east coast immediately below the border with Northern Ireland (Ó Baoill 1991). North of this line the accents are distinctly Ulster-like. South of this line the northern features rapidly give way to southern values. The term line here might imply a clearly delimited boundary, perhaps zone might be more accurate, as border counties such as Monaghan, Cavan or Louth show mixed accents which have adopted features from both northern and southern types.

The transition can be clearly seen moving down the east coast: Dundalk has a northern flavor to its speech but this is more or less lost by the time one reaches Drogheda travelling southwards. However, the recordings of A Sound Atlas of Irish English show that key features of northern Irish English, such as mid front vowel breaking, as in save [se:əv] , and /u/-fronting, as in boot  , extend quite far down the east coast, indeed in the case of the latter almost to the border of Co. Dublin.