At =79 m.= the route crosses the MISSOURI RIVER on the LEWIS AND CLARK BRIDGE, built in 1927, the second bridge in the State to span the Big Muddy. Natural gas from the Baker, Mont. field is piped into the Williston territory through lines that cross the bridge. South of the bridge the highway winds through the draws and ravines of the Little Badlands, a small area showing the results of severe erosion. At =96.5 m.= is the junction with a county improved road. Right on this road is CARTWRIGHT, =13.5 m.= (1,896 alt., 75 pop.), named for Samuel George Cartwright, the hunter-trapper who was its first settler. At =17 m.= is the YELLOWSTONE RIVER, the largest tributary of the Missouri, and an important factor in the history of exploration, settlement, and development of trade in Montana. Here, where the river joins the Missouri just within the North Dakota border, the valley once was a hunting paradise for the upper Missouri Indians, but fur traders, trappers, hunters, and settlers gave little thought to conservation, and the big game is now extinct. The three-million-dollar irrigation project completed in 1909 by the Federal Bureau of Reclamation has brought the region the title of Prosperous Valley. Sugar beets form the principal crop, although grains, vegetables, and forage crops are raised successfully, and there is some small-scale fruit farming. Center of the sugar industry is the refining plant at Sidney, Mont. (_see Mont. Tour 9_). The entire irrigated area contains 58,561 acres, of which 19,500 are in North Dakota. Sugar-beet acreage in the Yellowstone Valley in this State is approximately 1,800. Mexican labor is used in the beet fields; most of the Mexicans make their homes in the Sidney and Fairview, Mont. (_see below_) areas. The Yellowstone can be crossed here on the G. N. Ry. bridge, on which timber planking has been placed over the ties to permit automobile traffic. In one span of the bridge is a vertical lift to allow passage of river boats, although these are much more scarce than they were when the bridge was built in 1913. Just E. of the bridge is the only railroad tunnel in the State, a 1,456-foot timber-supported excavation piercing the soft earth hills bordering the Yellowstone. It serves a single track on a curved alignment of three degrees. At =21.5 m.= the road crosses the Montana Line at the city limits of Fairview, Mont. (_see Mont. Tour 9_). ALEXANDER, =98.5 m.= (2,146 alt., 386 pop.), was platted in 1905 shortly after organization of McKenzie County by special legislative act, and was designated temporary county seat by proclamation of Governor Sarles. Alexander McKenzie, political dictator of the early Dakota scene, was one of the town site incorporators, and both the town and county are named for him. Still standing is the old log building that served as the first county courthouse.