The parish of Hitterdal (later spelled Heddal) was established as a municipality on 1 January 1838 (see formannskapsdistrikt law). The municipality originally consisted of two parishes: Hitterdal with the Hitterdal Stave Church and Lilleherred with the Lilleherred Church (the spellings of the churches and parishes have varied historically). On 1 January 1913, the newly-designated kjøpstad (town) of Notodden (population: 4,821) was separated from Heddal to form a separate self-governing town as an enclave within Heddal Municipality. This left Heddal with 2,890 residents.[7]
During the 1960s, there were many municipal mergers across Norway due to the work of the Schei Committee. On 1 January 1964, Heddal Municipality was dissolved and the following areas were merged to form a new, larger Notodden Municipality:[7]
The municipality (originally the parish) is named after the Heddalen valley (Old Norse: Heitrardalr) since the historic Heddal Stave Church was built there. The first element is derived from the old name for the local river Heddøla, a tributary of the Skien River. The old name of the river comes from the genitive case of the word heitr which has an unknown meaning. The last element is dalr which means "valley" or "dale".[8] Historically, the name of the municipality was spelled Hitterdal or Hiterdal. On 3 November 1917, a royal resolution changed the spelling of the name of the municipality to Heddal.[9]
The municipal council(Herredsstyre) of Heddal was made up of representatives that were elected to four year terms. The tables below show the historical composition of the council by political party.
^Helland, Amund (1900). "Hitterdal herred". VIII. Bratsberg Amt. Anden del. Norges land og folk (in Norwegian). Kristiania, Norway: H. Aschehoug & Company. p. 399. Retrieved 27 August 2023.