Source: "Ohio, County Marriages, 1790-1950," index and images, FamilySearch (https://www.familysearch.org): accessed 30 July 2011. entry for William Smith and Prudence Maxson, married 5 October 1836; citing Marriage Records, FHL microfilm 466399; Clark County Courthouse, Springfield, Ohio.
Spent some time searching through Ohio marriage records database at FamilySearch and made a discovery - I had the date wrong in my database for the marriage of my paternal 3rd-great grandparents, William SMITH and Prudence MAXSON.
The image clearly shows they were married on the 5th of October 1836 in Clark County, Ohio. Previously, I had the date as the 3rd of October 1836 without knowing the county. Both the "Biographical and Historical Record of Jay County, Indiana (1887) and "The Maxson Family. Descendants of John Maxson and Mary Mosher of Westerly, Rhode Island" (1954) by Walter Brown had this incorrect date. Brown probably received his information from the 1887 history.
It was good to get the correct date, and even better to confirm the place of their marriage. Previously, I had searched Jay County, Indiana for a record - but their marriage date was too early for that county. The families were from the Clark County, Ohio area prior to the move to Jay County by the time of the 1840 census.
Now on to search for the rest of the families in Ohio...