From the record
“Bad Route Creek Bridge is a historic bridge which carries County Road 261 across the Bad Route Creek in Dawson County, Montana. The Security Bridge Company built the bridge on behalf of the Montana Highway Department in 1921-22.”
Wikipedia article Bad Route Creek Bridge, CC BY-SA 4.0.
One of 12 National Register listings published here for Dawson County · listed in 2011 · category: Structure · built in 1920.
Sources: the Wikipedia article · the case file at the National Archives · the National Register database, National Park Service