From the record
“The Lynnville Mill and Dam, also known as Wagaman Mill, is a historic complex located in Lynnville, Iowa, United States. John Sparks relocated from Lee County to Jasper County in 1845.”
Wikipedia article Lynnville Mill and Dam, CC BY-SA 4.0.
One of 16 National Register listings published here for Jasper County · listed in 1977 · category: Building.
Sources: the Wikipedia article · the case file at the National Archives · the National Register database, National Park Service