A patent for a federal land purchase was issued to Clark Sargent of Winnebago County, Illinois on 1 March 1848.
This is not evidence that he was alive on this date--it's the date the patent was issued by the Bureau of Land Management. He could have died while the paperwork was being processed. He was alive on the date he made the land purchase. But one cannot assume just based on this piece of paper that Clark was alive on 1 March 1848.