Mont. Code § 77-2-311
The board may cause any part of the lands bordering on lakes described in 77-2-303(2) and on navigable streams that are reserved from sale to be surveyed and platted into blocks and lots. The lots may not be less than 125 feet in width, measured in the general direction of the abutting water front, except that any former cabin or home sites proposed for sale or sold by the board may possess a width less than 125 feet. In all surveys and plats the strip of 100 feet in width along the water front, referred to in 77-2-303(2)(a), must be reserved for the use and enjoyment of the public. Cabin sites or home sites bordering on meandered lakes or navigable streams may be surveyed and sold consistent with the procedures provided in 77-2-361 through 77-2-367.
§ 77-2-311, MCA