[3] The parish of Solum was established as a municipality on 1 January 1838 (see formannskapsdistrikt law).

[4] Solum is located west of the town of Skien, and encompassed districts such as Nenset, Tollnes, Flakvarp, Skotfoss, and Klyve.

On 1 July 1916, an area of Solum Municipality (population: 1,042) was annexed by the growing town of Skien.

Then on 1 July 1920, a different area of Solum (population 1,614) was annexed by the growing town of Porsgrunn.

The last element is derived from the word heimr which means "village" or "abode".