The municipality encompassed most of the island of Halsnøy as well as some small surrounding areas.

The administrative centre was located in the village of Eidsvik on the island of Halsnøy.

[2] The parish of Eid was established as a municipality on 1 January 1838 (see formannskapsdistrikt law).

The name is the dative case of the word eið, which means "isthmus".

The name is referring to the fact that the old farm area was located on a narrow isthmus on the island of Halsnøya.