I have no further information on this family. I hope it helps someone.
Linda
THE HENNEPIN COUNTY MINNESOTA BIOGRAPHIES PROJECT
http://hennbios.tripod.com/index.htmHistory of Hennepin County and City of Minneapolis, 1881. North Star Publishing Co. Page 541
DUHNKE, William is a native of Prussia. He came to America in 1854; resided at Chicago one year; thence to Milwaukee remaining two years. He next made Indiana his home where he remained seven years, dealing in general merchandise, also kept the Tell City post-office. In 1866, he came to Minneapolis, and after being a dealer in crockery one year, opened the Mozart hall of which he is proprietor. He married Augusta Guhr in 1857. She died in 1871, leaving two children; William and Amelia. Mr. Duhnke married again, Annie Guhr, who bore him two children; Reinhold and Laura.