Another way to do it (since most of that awesome wide open ND space is void of wireless internet connection), go to the link (
North Dakota Travel Brochures) and order the free travel guide brochure. Then you have a hard copy with all the local campgrounds, etc. Suits my spontaneous style better. It is also available at rest areas along the way. ND is pretty friendly to travelers in this way. Hwy 2, aka the Highline, is a great route from Duluth MN to Bremerton WA.