The House of Commons (Method of Voting and Redistribution of Seats) Act (Northern Ireland) 1929 introduced first-past-the-post elections for 48 single-member constituencies (including Antrim South).

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.

The elections in this constituency took place using the first past the post electoral system.