Commercial airlines fly into the airports in two of Fort Union's gateway communities: Williston, ND, and Sidney, MT. In both communities, cars are available for rent.
Located on North Dakota 1804, the park is 25 miles southwest of Williston, ND, and 24 miles northeast of Sidney, MT. The park's west parking lot includes sufficient space for school and tour buses as well as RVs. The smaller east parking lot, which is closest to the fort, includes reserved spaces for handicapped or disabled parking.
From Williston, ND, take U.S. 2 West and follow the highway signs to North Dakota 1804. Turn left onto ND 1804 and then drive through the town of Trenton and passed Fort Buford and the intersection of North Dakota 58. The Fort Union entrance road will be on the left, or south, side of ND 1804 about 1.5 miles west of ND 58.
From Culbertson, MT, follow U.S. 2 East to Bainville, MT. Turning south out of Bainville on Secondary Route 327 leads to a scenic 15-mile drive on a gravel road that is NOT recommended, especially for motorcycles, bicycles, or RVs. The recommended route is to continue east into North Dakota and then, just past milepost 2, turning south, or right, onto the paved County Road 5. At the intersection with ND 1804 (after crossing the railroad overpass), turn right onto ND 1804. Proceed 2 miles west to the park entrance, which will be on the left, or south, side of ND 1804.
From Sidney, MT, drive east on Montana 200 through the town of Fairview and across the state line into North Dakota. Once through, or north of, Fairview, turn left onto North Dakota 58, which is at the first four-way intersection after crossing over the railroad tracks that bisect MT 200. Proceed north 10 miles to ND 1804 and, at the three-way intersection, make a left turn. The Fort Union entrance road will be on the left, or south, side of ND 1804 about 1.5 miles west of ND 58.
There is no public transportation that directly serves the park, but Amtrak's Empire Builder does stop in Williston, ND, where rental cars are available.