From the record
“The Moose Creek Administrative Site, in the vicinity of Grangeville, Idaho, was listed on the National Register of Historic Places in 1990.”
Wikipedia article Moose Creek Administrative Site, CC BY-SA 4.0.
One of 42 National Register listings published here for Idaho County · listed in 1990 · category: District.
Sources: the Wikipedia article · the case file at the National Archives · the National Register database, National Park Service