What Happened To Harvey?

I've written about a missing person in my family before, but I've only written in general terms, not specifics. (Anyhow, I am writing this in the hopes that someone might be able to suggest other areas I should look for information.)In fact, I did not even mention the name of the person that I am looking for, and since I did not do that in the first place, I'll start by giving the name of the person I'm searching for: Harvey Benjamin Oswalt.

What I know about Harvey

I don't know very much about Harvey, but here is what I know so far:

Harvey was born in December of 1861 in Michigan, according to his father's pension file, and was Adam's oldest son and child. In the 1870 census he was living with his parents, and his age was given as 10. (All the ages of the children were rounded up by a year.) Sometime between 1872 and 1880, Harvey's mother died. (I still do not know when she died exactly, but his youngest brother's biography suggests about 1875-1876 as a death year.) Between the 1870 and 1900 censuses, I do not know where he was. I cannot find him in the 1880 census, and I also checked the social statistics schedule for St. Joseph County, Michigan for him. Yet, I could not find him. In the 1900 census, I found him living in Three Rivers and working as a day laborer. After 1900, I cannot find him in any other federal censuses. All I know is that when Adam died in September of 1910, Harvey's youngest sister did not have a clue as to where he was.

Could some family traditions be clues to Harvey's whereabouts?

My grandfather's aunt apparently never told my grandpa about Harvey. She did mention, though, that Henry (another one of Harvey's younger brothers) supposedly went to New Mexico or Texas and died out there between 1925-1929. At the moment, I have only been able to prove that Henry lived as far west as Clinton, Iowa, and that Henry died in 1927 in Michigan. I sometimes wonder, though, if it was Harvey who went out west and died between those years as well. The other family story that my grandpa's aunt passed down was that there was an Oswalt who was a horse rustler. I have not been able to prove or disprove this family legend, but I sometimes wonder if she was referring to Harvey.

Some possible records I could look for Information

• 1884 Michigan State census - I've looked for other Oswalt family members in this census, but I have not done so for Harvey. My first guess as to which county to look at is St. Joseph County.
• 1894 Michigan State census - I still have not checked this census for any of my Oswalt family.
• Other state censuses - I might need to the state censuses for Illinois, and see if any censuses for the 1880s and 1890s exist. Why? Adam and his son, Henry, lived in Rockford, Illinois sometime between the late 1880s and 1890s. (Henry continued to live there until 1910.) Could Harvey have moved out there with them?
• Probate packet - I still have not had a chance to obtain Harvey's probate packet in the St. Joseph County, Michigan's probate office. All I know is that the reason for the packer is given as missing. (I hope to be able to get a copy of the packer sometime in the future.)
• Other records - I'm not sure what other records I should check. The only record source that I can think of is court minutes for St. Joseph County, Michigan. I'm at a loss as to obtain or find the court minutes. Does anyone know how to obtain court minutes? Other than that, I have no idea as to what records I should look at.

Which record should I look through first? Any suggestions or advice is welcome. Thanks.