U.S. Route 85 (US 85) is a part of the U.S. Highway System that travels from the Mexican border in El Paso, Texas, north to the Canadian border north of Fortuna. In the state of North Dakota, US 85 travels from the South Dakota state line south of Bowman north to the Canadian border.
US 85 enters North Dakota in the southwest part of the state. The first city on its route is Bowman at the junction of US 12. Continuing north, it passes between North Dakota's two highest points, White Butte and Black Butte. Near Amidon US 85 heads east for before going back north and junctions ND 21, along the Little Missouri National Grassland for about . In Belfield it junctions with Interstate 94 (I-94), about 15 miles east of Medora and the Theodore Roosevelt National Park (South Unit). North of Belfield, US 85 passes through the unincorporated community of Fairfield. It meets North Dakota Highway 200 south of Grassy Butte. After running concurrently with ND 200, it eventually passes through part of the scenic Badlands, crosses the Little Missouri River at the Long X Bridge and passes near the Theodore Roosevelt National Park (North Unit).
Then, at Watford City it travels west for past Arnegard and Rawson, until it junctions with ND 68, where it turns back north, while ND 68 turns south and then west towards Sidney, Montana, before Alexander. US 85 bypasses Alexander while US 85 Business serves the city. US 85 continues north as ND 200 turns west toward Montana. South of Williston it crosses the Missouri River. The stretch from Watford City to Williston is in the process of being converted into an undivided four-lane highway, and it should be substantially completed in 2014. A few miles later, it meets with US 2 west of Williston. US 85 continues as an expressway that bypasses Williston to the northwest near the Williston Basin International Airport, while US 2 goes into Williston. After US 2 heads east towards Minot, US 85 continues north to a concurrency with ND 5. From there it is to Fortuna where US 85 heads back north for its remaining to the Canadian border.
In October 2024, US 85 from Interstate 94 to the Watford City bypass became four lanes. The North Dakota Department of Transportation is working on a plan to expand the south segment of U.S. Highway 85 from two to four lanes.