He was the son of a ship manager Johan Christian Tønsberg (1788–1830) and Anne Marie Dahl (1788–1837).
[2] Tønsberg was employed as clerk in the Treasury Department, working in the office of several Supreme Court lawyers.
Tønsberg also served as consul for several countries: Kingdom of Bavaria, Grand Duchy of Mecklenburg, Colombia, Liberia and Romania.
He also published works of Andreas Munch, Mauritz Hansen, Magnus Brostrup Landstad, Rudolf Keyser, Nicolay Nicolaysen and Ludvig Daae among others.
[3] [4] Tønsberg became strongly influenced by the National Romantic period and was eager to establish a co-operation between the different art forms.