I am a life long resident of ND. Where do I start. Well the west has the Badlands (best seen late May early June very pretty land) easy access to the south unit of Theodore Roosvelt Park but the north unit up Highway 85 is more scenic). Bismarck is our capital and situate on the Missouri River, it has several attractions, the State Capital (know as the sky scraper on the praire), the heritage center (North Dakota history) and Fort Abraham Lincoln (the fort Custer stayed at before the battle of Little Big Horn). As you head east you will realize the land changes and before you know it you are in the Red River Valley a area where in place the elevation doesn't change more then a foot in 60 miles. On the eastern edge there is the largest town of Fargo (180,000).
Depending on your wants ND can probably provide.
Camping is available all over
Fargo, Bismarck, Grand Forks and Minot all provide for arts and entertainment.
Hunting and Fishing is abundant
the air is clean and the sky at sun set is gorgeous
There's always the Peace Gardens - celebration of the longest unfortified border between two countries in the world. International Music Camp meets near there, so if you go in the summer, you can take in some nostalgic-for-high-school concerts.
The Badlands any time of the year. See where Teddy became a man. Also check out the house the Marquis de Mores left behind.
If you are a hunter, best waterfowl hunting in Midwest. Good pheasant hunting in certain areas.
The Badlands are definitely worth visiting any time of the year. We also have great waterfowl hunting in the fall if that's something that interests you.
I guess it depends on what time of the year you want to visit. There are many nice places to go there as I lived in ND for 40 years. The western part of the state is very scenic.