From the record
“Campbell's Ferry was a ferry crossing on the Salmon River, located at Mile 148 of the river in the Frank Church-River of No Return Wilderness. The ferry was part of the Three Blaze Trail, which connected Grangeville to Dixie, Idaho, to the Monumental Creek Trail at Thunder Mountain.”
Wikipedia article Campbell's Ferry, CC BY-SA 4.0.
One of 42 National Register listings published here for Idaho County · listed in 2007 · category: District.
Sources: the Wikipedia article · the case file at the National Archives · the National Register database, National Park Service · the Wikipedia article