Elm Hall is worth checking out just to see the tiny post office!
From Wikipedia
Elm Hall is an unincorporated community and census-designated place (CDP) in Gratiot County in the U.S. state of Michigan. The CDP had a population of 165 at the 2020 census. The community is located within Sumner Township.
As an unincorporated community, Elm Hall has no legal autonomy of its own but does have its own post office with the 48830 ZIP Code.
Elm Hall was first settled in 1855 by brothers Jacob, Michael, and Nathaniel Strayer and their families. Sumner Township was established that same year. The families all lived in a long building (or hall) that was made out of elm logs, and the community name became known as Elm Hall. A post office was established on August 18, 1857 with Baron Blanchard serving as the first postmaster. The community was platted and recorded in 1863.
For the 2020 census, Elm Hall was included as a newly-listed census-designated place. Elm Hall continues to remain an unincorporated community with no legal autonomy of its own.