The town was founded in 1849 and named after British Governor Harry Smith, who tried to persuade the Voortrekkers not to abandon Natal.
The town was initially laid out by Robert Moffat about 25 km from the present location, in present day Aberfeldy on the Elands River. This site unfortunately proved to be deficient in water and Harrismith was shifted to its present site in January 1850. Twenty-four years later it became a municipality and during the diamond rush at Kimberley, the town became a busy staging post on the Natal transport route. As a direct result of this, hotels, stores and public buildings sprang up. Harrismith was a major base during the South African (Anglo-Boer) War and visitors can see the several blockhouses, engineering works and a military cemetery that are evidence of this.
The town's main street, Warden Street, is named after Major Henry D. Warden, at that time a British resident in Bloemfontein.
The town is around 90 kilometers west from Ladysmith, a town named after Sir Harry Smith's wife that is located in the KwaZulu-Natal province. It is a similar distance east of Bethlehem
The small nearby hamlet of Swinburne is named after Sir Johan Swinburne, a gold prospector
