Grästorp Municipality is located right in the middle of Västra Götaland County, by the shores of Lake Vänern.

In the year 1900 the village Grästorp was detached from Tengene and made a market town (köping).

The local government reform of 1952 amalgamated it with twelve surrounding municipalities (among them Tengene).

The 1971 reform made the term köping obsolete, thus forming Grästorps kommun without amendment of territory.

The runestone at the church at Sal has an inscription that reads "Torgård satte denna sten efter Toke, sin frände", meaning "Torgård raised this stone for Toke, his kinsman".