Wyoming leap-frogged from one of the smallest growing states in 2012, to one of the fastest growing states in 2013, all because of big growth in its mining sector.

Wyoming is a major coal producing state, accounting for about 40% of all coal mined in the United States.

For several years, this heavy reliance on just one industry was the state's main weakness. Natural gas prices were low and power plants started making the switch away from coal.

That changed in 2013 though, as natural gas prices rose and coal became the cheaper alternative. Demand for Wyoming coal returned, and so too did the state's economy.

Going forward, Wyoming needs to diversify its economy, so it's not so reliant on just this one industry.