Idaho Code § 31-805: Supervision of roads, bridges, and ferries.

The board shall lay out, maintain, control and manage public roads, turnpikes, ferries and bridges within the county, and levy such tax therefor as authorized by law; provided that the board need not lay out, maintain, control, and manage public roads, turnpikes, ferries, and bridges inside the boundaries of a highway district formed pursuant to title 40, Idaho Code.