I thought I would try to dig up some more information on my great great grandfather. Since I don't have a primary source for his birth, I thought I'd try to find a birth record of some sort. According to all the documentation I have, he was born in Wisconsin. The 1870 federal census puts the John living with his parents in the town of Kendall, Lafayette County, Wisconsin.
I consulted my Resource Book for Genealogists and discovered that pre-1907 birth records are indexed and available through the Wisconsin Historical Society. Luckily, the WHS has a website! (http://www.wisconsinhistory.org/genealogy/)
Just to be on the safe side, I did a search on http://uscitydirectories.com/ to see if maybe I could find his family in Kendall or Lafayette County. I even looked for Darlington, which is now the county seat of Lafayette County. Nothing. If anyone has a link to a website that has city directories for Wisconsin indexed, please let me know!
Since I seem to be striking out on the birth record, I guess I'll search for the record of John's marriage to Theresa Burns. Remember the South Dakota state census said that they were married in 1886, but we don't know when. I headed over to GenWed (http://www.genwed.com/) to see if they had any records for Yankton County, South Dakota. Nada. Well, I'm just not getting anywhere today. Looks like I'm going old school. Snail mail.
I did a search for the Register of Deeds for Yankton County, and I will give them a call on Monday and find out their fees, etc. and send a letter. While I'm waiting for that information to arrive, I'll try to solve another mystery: where is John buried?