From the record
“Day House near Stanley, Idaho is a c.1936-built Rustic style log cabin also known as Doc Day Cabin. It was listed on the National Register of Historic Places in 1986.”
Wikipedia article Ivan W. Day House, CC BY-SA 4.0.
One of 33 National Register listings published here for Custer County · listed in 1986 · category: Building.
Sources: the Wikipedia article · the case file at the National Archives · the National Register database, National Park Service