Sometimes all you really need to do to have decent air is not have lots of people. That's certainly the case in North Dakota, which has fewer than 10 people per sq. mi. As North Dakota cities go, Dickinson is on the large side, with over 15,000 people still not enough to besmirch the air. But there may be problems in the future federal and state officials are fighting over hazy air in nearby Theodore Roosevelt National Park.
Next Farmington, N.M.