Buck Polygonal Barn was a historical structure located near Diagonal in rural Ringgold County, Iowa, United States.

[3] The structure of the barn was basically a central octagon with a sectioned roof.

Double pitch sheds surrounded the barn characterizing it as an encircling wing type.

The plan appears to be the same as the one for the Lloyd Z. Jones stock barn published in Wallaces' Farmer on January 16, 1903, and again on October 25, 1907, and June 17, 1910.

This article about a property in Ringgold County, Iowa on the National Register of Historic Places is a stub.