Responders, Thank you for the various responses. The person in question knew well how to read and write and made the change himself. The census takers and immigration agents did make many a mess of names but obviously had to be told to add an m to Arm. No one would naturally do it. This change was clearly intentional on the part of John Armm. His brother had the same name as his father, Samuel, so it wasn't for name confusion. I think Arm was uncommon in Jackson County, there was no mail delivery confusion. His father remarried after the mother's death but that was very common and usually didn't bother the grown children enough to change their name over it. He wasn't the oldest so not in line to inherit the Ohio farm anyway. Maybe he just wanted to be different. I was hoping if it had been legally changed, a reason might have been given. A little research through Google only found articles on current law relating to gay marriage, sex changes, adoption and divorce. Immigrants changed their names to blend in, but John Arm was OK on that front and wasn't an immigrant. So why did he do it? There are published books covering name changes from 1866-1893 in California, 1800- 1856 in Georgia, to 1852 in Indiana, 1634-1854 in Maryland, from 1780 to 1892 in Massachusetts and from 1790-1892 in North Carolina. Supposedly every state had a mechanism for changing one's name. Illinois must have had a legal way to change the name, but since all legal actions cost money, maybe he didn't bother. He was not a rich man. You all may be right. Maybe he just decided to change it and no one questioned it. They only knew him in Illinois, not his family back in Ohio. They probably took him at his word. All of his nine children and many grandchildren are dead so I may never know why he did it. Still curious. Many thanks. Shirley Maul