Mont. Code Ann. § 7-14-2803

When a petition to a board of county commissioners indicates that it is necessary to establish and maintain a public ferry across or a wharf at any unfordable stream, lake, estuary, or bay, the county, through its board of county commissioners, may construct a ferry or wharf or may purchase or acquire a ferry or wharf by condemnation, as provided in Title 70, chapter 30, and may operate and maintain a ferry across or a wharf at any unfordable stream, lake, estuary, or bay within or bordering the county. The county may also acquire, operate, and maintain all the necessary boats, grounds, roads, approaches, landings, and improvements pertaining to the ferry or wharf. The county may operate the ferry or wharf for free or may charge for the use.