The Civil Registers are compiled in local registration districts/offices. Attached is a link to the Irish Times/Irish Ancestors website with a map of the historical registrations districts as a guide:
Please note that within the districts you also had local registration offices which are reflected in the earlier returns shown. In all instances these covered a certain locality and do not denote the specific place of Birth, Marriage or Death. That information can be found on the full certificate or copy of the register entry.