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This constituency was one of seven county divisions in County Antrim from 1929, and, after 1969, one of nine. The changes in the vicinity of Belfast affected the boundaries of this division.
It comprised (in terms of then local government units) part of the rural district of Lisburn and the whole of the urban district of Lisburn. In 1969, the part of the rural district closest to Belfast became the new seat of Antrim, Larkfield.
County Antrim (except for parts of Belfast) is a strongly unionist area. There was never the slightest chance of a republican or nationalist candidate being elected in a single-member Antrim county constituency. Antrim South was not an exception.
From the Northern Ireland general election of 1929, the Antrim South division was an extremely safe Unionist seat for the rest of the existence of the Northern Ireland Parliament.