ShotHotspot has mapped 6 abandoned places in Custer, Idaho, ranked by how often they're photographed, viewed and voted for. The most popular are Barn Reduced Runoff Capacity, Abandoned Bayhorse Ghost Town and Ruins of the old ghost town of Bayhorse Idaho, in the Salmon Challis National Forest. Some are private property or unsafe, so get permission before you visit.
We don't know whether you're allowed to visit any of these places. Many are private property, closed to the public or unsafe: get permission from the owner or the relevant authority, and take safety precautions.
ShotHotspot is a search engine for photography locations: it maps where people take photos, worldwide, from millions of geotagged photos. Browse by country, abandoned places, guides.