The state 's two fastest growing counties are : `` Summit '' ( at 91.6 percent ; ranking it 8th in the country ) and `` Washington '' ( at 86.1 percent ; ranking it 12th ) . The state 's two fastest growing counties are : Summit ( at 91.6 percent ; ranking it 8th in the country ) and Washington ( at 86.1 percent ; ranking it 12th ) .