The main population centre of Sannidal was the village of Kil, which is situated at the end of the Kilsfjord.

For this reason it was one of the earliest settlements in the area, being an important link between the sea and the land.

Exports of timber dating from 1600s-1700s gave the area a good income and made Kil the first commercial center for Sannidal and surrounding country.

The parish of Sannikedal (later spelled Sandøkedal or Sannidal) was established as a municipality on 1 January 1838 (see formannskapsdistrikt law).

On 3 November 1917, a royal resolution changed the spelling of the name of the municipality to Sannidal.