After Sweden conquered the parishes of Idre and Särna in 1644 the lake Femunden was considered to be the border between Norway and Sweden.
The 1645 Treaty of Brömsebro was ambiguous regarding the status of the parishes, but when the exact path of the border was to be decided in 1751 Norway accepted a border west of Idre and Särna.
The name was referring to the valleys of the rivers Glomma, Rena, Trysilelva and Österdalälven (the parishes Idre and Särna belonged to Norway until 1644).
Idre |