After obtaining his doctorate in 1962, he became Wissenschaftlicher Assistent at the Chair of Schleswig-Holstein and Nordic History.
[2] From 1998 until his death he chaired the Board of Trustees of the Institute for Schleswig-Holstein Contemporary and Regional History at the University of Flensburg.
"[4] His research was focused on the history of Schleswig-Holstein, especially on historic canal projects from the Eider Canal to the Kiel Canal, the constitutional and national movement of the country in the 19th century, the history of German-Danish relations since the time of Enlightened Absolutism, including minority and borderland issues, as well as the period of the Weimar Republic and Nazi Germany in particular with regard to the history of the University of Kiel.
[5] Jessen-Klingenberg is best known for his research on the proclamation of the Republic by Philipp Scheidemann on 9 November 1918.
With his essay published in 1968, he has provided the narrative about this event that is still predominant in historical scholarship today.