The valley is surrounded by wooded hills which rise up towards 500-metre (1,600 ft) tall mountain peaks.

On 1 January 1968, the unpopulated Svartangen area of Siljan was transferred to Hedrum (and Vestfold county).

On 1 January 1974 the unpopulated Tagtvedt area of Hedrum was transferred to the neighboring town of Larvik.

On 1 January 1983, the unpopulated Bergan area of Hedrum was transferred to the neighboring Lardal municipality.

On 1 January 1986, part of the Åsveien 3 property in Hedrum was transferred to the neighboring town of Larvik.

The official blazon is "Vert, a bend wavy argent" (Norwegian: På grønn bunn en sølv skråbjelke dannet ved bolgesnitt).

This means the arms have a green field (background) and the charge is a wavy diagonal line.

The charge has a tincture of argent which means it is commonly colored white, but if it is made out of metal, then silver is used.

Some of the graves are believed to pre-date the introduction of Christianity confirming the supposition that ancient pagan cult sites were chosen as the venue for the earlier churches.

[13] The municipal council (Kommunestyre) of Hedrum was made up of representatives that were elected to four year terms.