I had seen family trees documenting the marriage of Hannah (Birge) and Dudley Lyford Cass, my 3rd great grandparents, as having taken place in a variety of places and with several different dates.
Based upon one tree found online that indicated they were married in Conant, Ohio, I found the 1840 US Census which indicates Abraham, my 4th great grandfather, was living in Conneaut, Ashtabula County, Ohio. Using that information as a guide, I located the Ashtabula County genealogy website.
From their website, I located their marriage index of microfilm from 1811 - 1900 which confirms that Hannah (Birge) and Dudley Lyford Cass were married in Ashtabula County, Ohio in 1847.
For anyone that would like to order a copy of the microfilm verifying the marriage information, please order through the Ashtabula County Genealogical Society by clicking on the link above.
Having found the marriage information, I now know the Cass family moved from Ohio to Jefferson County, Wisconsin sometime between 1847 and 1850.