Like his father, he studied law, graduating as cand.jur. in 1826. In 1833 he was hired as an attorney in Fjaler,[2] where his father was seated as the district stipendiary magistrate (sorenskriver) of Sunnfjord. Johan was given the property Fagervik, previously a part of his father's farm Tysse. He lived at Fagervik from 1833 to 1846. In 1847 he was appointed bailiff (fut) in Sogn, and moved to Balestrand Municipality.[2]
Johan Widing Heiberg Landmark had a political career. When local governance was introduced in 1837, he became the first mayor of Ytre Holmedal Municipality. In 1845 he served as a deputy representative to the Norwegian Parliament.[2]
He died in Balestrand.[1]
