North Fork is an unincorporated community in Lemhi County, Idaho. Its name is derived from confluence of the south-flowing North Fork of the Salmon River with the north-flowing main Salmon River, which makes a near-right angle turn here to flow westward across the state to Riggins. US 93 serves the community, connecting it with Salmon to the south an…North Fork is an unincorporated community in Lemhi County, Idaho. Its name is derived from confluence of the south-flowing North Fork of the Salmon River with the north-flowing main Salmon River, which makes a near-right angle turn here to flow westward across the state to Riggins. US 93 serves the community, connecting it with Salmon to the south and Lost Trail Pass to the north.