Here is the 1880 US Census for my 3rd great grandparents, Hannah (Birge) and Dudley Cass, still living in Hancock, Waushara County, Wisconsin.
My 2nd great grandfather, James Hardy Cass isn't listed as a member of the household. He would marry Mary Ware the following year. The Ware family was also still living in Hancock (the following census page) but Mary was not listed.
I did find another 1870 US Census for a Hardee Cass living a few miles away in Plainfield, Wisconsin, which is only a few miles from Hancock. This Hardee is listed as being 18 years old. The 1870 Census posted yesterday indicated Hardy was 17.
Hardy was already listed as living with his parents in Hancock on the 1870 US Census as of June 22nd before the Plainfield census was conducted on July 15th.. I'm not sure whether this is the same James Hardy Cass and he just moved within that time frame, but looking through the 1880 Census in Plainfield, Wisconsin I still couldn't locate his or Mary's whereabouts.