From the record
“Aggergaard Manor is a historic house in Irene, South Dakota. It was designed in the Colonial Revival style, and built in 1904 for Peter N.”
Wikipedia article Aggergaard Manor, CC BY-SA 4.0.
One of 78 National Register listings published here for Yankton County · listed in 2001 · category: Building.
Sources: the Wikipedia article · the case file at the National Archives · the National Register database, National Park Service