[6] She was a granddaughter of Hieronymus Heyerdahl,[7] Mustad started his working career in 1857, when hired in his father's company.

In 1875, the company bought property at Lilleaker in Kristiania (now Oslo), adjacent to the Lysaker river.

With a nearby waterfall at Fåbrofossen, this location had a history of industry stretching back to the nail works owned by poet Christian Braunmann Tullin, which existed from 1749 to 1830.

[8] In 1889, the foundry was moved to Lilleaker, and the same year a margarine factory was established, entering a new branch of business.

[5] By that time, O. Mustad & Søn was the largest industrial company in Norway, with 2,000 domestic employees as well as several factories abroad.