From the record
“The Harding Schoolhouse, in Corson County, South Dakota near Trail City, was listed on the National Register of Historic Places in 1989.”
Wikipedia article Harding Schoolhouse, CC BY-SA 4.0.
One of 4 National Register listings published here for Corson County · listed in 1989 · category: Building · built in 1931.
Sources: the Wikipedia article · the case file at the National Archives · the National Register database, National Park Service