I would like to add two more options:
- For anything concerning the history of Husum (whereabouts of buildings like a hospital), the "Verein für Stadtgeschichte" (A society working on the local history) might help:
http://www.husumer-stadtgeschichte.d...impressum.html (this page is in german, but there are two contacts there)
- Is your mother baptized? Then the register at the local church might help.