Minnesota's First Post Office

Minnesota's first post office was at Fort Snelling. It operated from 1827 through 1918. Fort Snelling was abandoned as a military installation after World War II. It is still open for tours and reenactments. It is one of a handful of post offices that were operating prior to the establishment of the Minnesota Territory. I know Stillwater, St. Paul, Wabasha(w) all opened in the 1840's. I'm sure there are others.
I don't have any territorial or pre-territorial covers from Fort Snelling. In the picture below the first cover is from 1917 which was one year before the post office closed.
Fort Snelling has  had two days that they were open for special cancellations . One was for the First Day of Issue for the six cent stamp commemorating the Sesquicentennial  of Fort Snelling.
The second cover has signatures from most of the notables that were at the ceremony. Many of these men were instrumental to getting the First Day ceremony held at Fort Snelling. I don't know who all the signatures are from. If you know please leave it in the comment section. Wayne Hassell was a stamp dealer that also wrote a stamp column for the Tribune. Floyd Risvold wrote "the" book on Minnesota Postal History. Les was the artist.
The third cover is signed by the governor at the time, Harold LeVander.