Franklin County was the fastest-growing county in the state between 2018-19, with Benton County nipping close behind at No. 3.Kennewick ranked No. 5 in the state for population growth, adding 1,820 people; Pasco ranked No. 8, adding 1,700 people; Richland ranked No. 11, adding 1,530 people.The Tri-City area’s population grew...