From the record
“Marsh Concrete Rainbow Arch Bridge is a reinforced concrete through arch bridge over the Little Cottonwood River in Cambria Township, Minnesota, United States. The bridge is listed on the National Register of Historic Places.”
Wikipedia article Marsh Concrete Rainbow Arch Bridge, CC BY-SA 4.0.
One of 28 National Register listings published here for Blue Earth County · listed in 1980 · category: Structure.
Sources: the Wikipedia article · the case file at the National Archives · the National Register database, National Park Service