From the record
“The Gramberg Ranch, in Pennington County, South Dakota near Hermosa, was listed on the National Register of Historic Places in 1999. The listing included eight contributing buildings, six contributing structures, and four contributing sites.”
Wikipedia article Gramberg Ranch, CC BY-SA 4.0.
One of 59 National Register listings published here for Pennington County · listed in 1999 · category: District.
Sources: the Wikipedia article · the case file at the National Archives · the National Register database, National Park Service