Nina is correct-and you should also use the same trick in checking the census records. If he died prior to the 1870 census, you can look for either a child or widow as head of household.

In the case of all records of the period, it's a combination of factors. 1. The understanding of the name by the census taker/army recordkeeper, 2. The education and spelling ability of all parties-including the person bearing the name, 3. Local variations of the same name may alter how it shows up. Be creative-Simons/Symons/Simmons/Simones/Cymons, etc.