Limestone occurs in thick formations near Lava Creek, and in the valley of the East Fork of the Yellowstone river; also near the summit of the Owl Creek range, and in the Wind River range.
The Yellowstone is navigable for about 300 m.
Among the larger privately irrigated tracts are: 16,000 to 18,000 acres in Yellowstone county, fed by a canal built by the Billings Land & Irrigation Company; about 35,000 acres of orchard land in the Bitterroot Valley, in Ravalli county, irrigated by canals from Lake Como, a natural reservoir; and 100,000 acres in Missoula county, to be watered from a 28 ft.
Among them are: the Huntley project in Yellowstone county, begun in 1904 and practically completed in 1908, covering land formerly in the Crow Indian reservation, the irrigable area being 28,921 acres; the Lower Milk river project (and the subsidiary St Mary project), in Chouteau, Valley and Teton counties, by which the water of St Mary river 1 is stored and diverted to the headquarters of the Milk river to irrigate an area of 300,000 acres; the Sun river project (Teton, Lewis and Clark, Chouteau and Cascade counties), by which, as the ordinary flow of that river is already utilized for irrigation, the flood waters are stored and carried to the higher bench lands of the district; in Montana (Dawson county) and North Dakota (McKenzie county), the Lower Yellowstone project; and the Blackfeet project, to irrigate the Blackfeet reservation in Teton county.
The principal sheep-raising counties are Custer, Yellowstone, whither many sheep are brought to be fattened, Rosebud, Beaverhead, Valley, and Meagher.