This is an instance where a search of the 1880 U.S. census online may be beneficial. Go to: http://www.familysearch.org Click on the census link on the left side of the page. On the next page, select the 1880 U.S. census in the top box, and you can then customize your search. A phonetic search of Katz/Kaatz with census results for Wisconsin would probably be the first search to make. If you get a lot of results, you could refine the search for results for Dunn County. Good luck! -- Adele/Seattle