Looking for Clark Sargent of Winnebago County, Illinois

Clark Sargent purchased federal land in Winnebago County, Illinois on 1 March 1848. I think he died shortly thereafter and the Mrs. Mary Sargent that married in Winnebago County, Illinois to Asa Landon on 6 January 1849 is his widow. I have tracked Mary and Asa in the 1850 (Winnebago County, Illinois) and 1860 census (Christian County, Missouri), but am trying to find out if Clark Sargent who purchased the property is the Sargent who was the husband of Mary. One of the Sargent children living with Landon is Ira, born ca. 1844. I lose the Landons after 1860.