From the record
“The Polson Feed Mill is a site on the National Register of Historic Places located in Polson, Montana. It was added to the Register on April 29, 1980.”
Wikipedia article Polson Feed Mill, CC BY-SA 4.0.
One of 9 National Register listings published here for Lake County · listed in 1980 · category: Building · built in 1910.
Sources: the Wikipedia article · the case file at the National Archives · the National Register database, National Park Service