It encompassed about 200 square kilometres (77 sq mi) in the southern part of the present-day Vestnes Municipality.

The municipality included the Skorgedalen valley and the area surrounding both sides of the southern half of the Tresfjorden.

The main village in the municipality was located at the head of the fjord and it was also named Tresfjord.

This name is probably derived from the word træsa which means "to walk restlessly back and forth" or "to trot about".

[7] The municipal council (Heradsstyre) of Tresfjord was made up of representatives that were elected to four year terms.