[1] Lorentz Johannsen was born at Glücksburg in the district of Schleswig-Flensburg in Schleswig-Holstein (now in Germany).
Both of his wives were daughters of Hans Carl Knudtzon (1751-1823) who was a successful merchant in Trondheim, Norway.
Hans Carl Knudtzon had been born in Bredstedt, in the district of Nordfriesland, Schleswig-Holstein.
Following his marriage, Lorentz Johannsen became a partner with his father-in-law at the trading firm.
The firm operated its own fleet of ships and was engaged in the trade of commodities.