From the record
“The James Greer McQuilkin Round Barn is a historic building located near Eagle Center in rural Benton County, Iowa, United States. It was built in 1918 for James Greer McQuilkin.”
Wikipedia article James Greer McQuilkin Round Barn, CC BY-SA 4.0.
One of 17 National Register listings published here for Benton County · listed in 1986 · category: Building.
Sources: the Wikipedia article · the case file at the National Archives · the National Register database, National Park Service