Here is an interesting article from Portland's Oregonian about a couple who is trying to adopt the Arrah Wanna Road Bridge over the Salmon River. I wish them luck on the endeavor.
On a side note related to the article, I browsed the ODOT records and found the standard drawing that dates from 1911 for this type of pony truss. These standard drawings pre-date the 1913 creation of the highway department and were developed by the Coast Bridge Company of Portland, Oregon. Thanks to this, I believe I can now trace this standard design to at least a couple of different pony truss bridges in the state.
Another step forward in determining the origin of these turn of the century relocated trusses!