From the record
“The William Ingersoll Estate is a former summer home complex on an island in Sand Point Lake in the U.S. state of Minnesota, in what is now Voyageurs National Park. Ingersoll (1885-1973) was a wealthy philanthropist from Canton, Illinois.”
Wikipedia article William Ingersoll Estate, CC BY-SA 4.0.
One of 126 National Register listings published here for St. Louis County · listed in 2011 · category: District · built in 1928, by E. F. Hodgson Co.
Sources: the Wikipedia article · the case file at the National Archives · the National Register database, National Park Service