The best and worst things about North Dakota are linked. The oil boom was the best thing that's happened there for years. Between 2011 and 2016, development at the Bakken shale oil formation pushed the state's GDP up by a massive 25%.
Just as oil gives, though, oil takes away. In more recent years, the price of oil has stagnated, and the economy is sliding back down again. The 5% drop last year was the worst performance of any American state.