 The constituency was created by the Redistribution of Seats Act 1885 for the 1885 general election, and abolished for the 1918 general election.Eifion covered the southern part of Caernarvonshire.It included the Sessional Divisions of Eifionydd (or Portmadoc) and Pwllheli (excluding the boroughs of Caernarvon and Pwllheli and the parishes of Criccieth and Nevin) and part of the Sessional Division of Caernarvon (excluding the parishes of Llanberis and Llanddeiniolen).