Particularly noteworthy are the records of the noble house of Letmathe (documents from the 14th century onwards) as well as those of nationally known companies and families. Examples are the company Kissing & Möllmann with worldwide trade relations, among others to South America and Eastern Europe, as well as the family estates of Löbbecke, Möllmann and Nohl.
In a reference library, the city archive also has literature on local, regional and national history.
A series of lectures provides insights into the history of the city, and the results of the archive's work are presented in publications, exhibitions and guided tours.
Interested citizens can view the largely unique archive and collection material in the reading room of the city archive in the "Alte Post".
A microfilm reader is also available.
If the state of preservation of the documents allows it, photocopies or own digital recordings can be made.
Documents, photographs and postcards relating to Iserlohn are gladly accepted to expand the archive holdings.