try using the search site familysearch.org if you want Minnesota records. They have census records for 1870, 1880, 1885, 1895, 1900, 1905, 1910, 1920, 1930, and 1940. There are also death records for deaths after 1900. There might be naturalization (citizenship records).
The belt of the uniform does say US, and maybe it is a legitimate uniform - many immigrants from all over the north, including Minnesota did join the army in the civil war. Then after the war, those soldiers were able to homestead land in Minnesota, and had an advantage. Instead of having to firm up their homestead (free farm land) by staying on the land and making improvements for the required 5 years, they could count their years in the army towards that five year requirement, and own the land much sooner. I do see from searching that there were also Hesse families living in New Ulm Minnesota area in that time frame, which was a big German settlement too, although German settlements were all over the state. The spelling Hessie could also be used.