He later relocated to Lærdalsøyri, and became the most significant merchant and landowner there. Much of his real estate was bought at an auction in 1828. He also bought a number of ships, which were kept in traffic between Lofoten and the Baltic Sea.
He founded the transport company Nordre Bergenhus Amts Dampskibe (later known as Fylkesbaatane i Sogn og Fjordane) with Harald Ulrik Sverdrup and Michael Aubert in 1858, and was also director of the local savings bank.
January Henrik Nitter Hansen was also involved in politics. He served as mayor of Lærdal municipality from 1844 to 1845 and 1848 to 1857, and served as a deputy representative to the Norwegian Parliament in 1851 and 1854.