From the record
“The Murphy Trail and Bridge in San Juan County, Utah, United States, were used to move livestock from winter range along the Green River to highland summer range from about 1917 to about 1964. The trail and bridge are located in what is now Canyonlands National Park and the trail is now used as a hiking path.”
Wikipedia article Murphy Trail and Bridge, CC BY-SA 4.0.
One of 23 National Register listings published here for San Juan County · listed in 1988 · category: District · built in 1917.
Sources: the Wikipedia article · the case file at the National Archives · the National Register database, National Park Service