From the record
“The East Soldier River Bridge was located southwest of Charter Oak, Iowa, United States. It carried traffic on 120th Street over the East Soldier River.”
Wikipedia article East Soldier River Bridge, CC BY-SA 4.0.
One of 15 National Register listings published here for Crawford County · listed in 1998 · category: Structure.
Sources: the Wikipedia article · the case file at the National Archives · the National Register database, National Park Service