The bio page has a confusing comment.
is likely to be the US civil war veteran (listed as a member of 4th Regiment, Missouri Infantry - Company B - mustered at Howell County, Missouri to serve the confederacy)
There is a record for William Black in the 4th Missouri Cavalry CSA. There is only one record that says he deserted in Aug 1863.
Missouri was a confusing state---it was divided between Union and Confederate and a lot of guerrilla fighters.
If he deserted he could have joined a Union regiment from Missouri. I checked and there are dozens of Wm Black in Union regiments.
Another option is that a Confederate prisoner who wanted to fight for the Union were assigned to a US regiment and sent out West to fight the Indians. There are a lot of regiments to search through.
Also, the company he was in with the 4th Missouri Cav CSA was originally called Preston's Battalion. Sometimes, you can go to the records for the original unit and find more info, but I checked it and there were no Black's.
Need more info.