Rock Island County, Illinois

Rock Island County is a county located in the U.S. state of Illinois, bounded on the west by the Mississippi River. According to the 2010 census, it had a population of 147,546. Its county seat is Rock Island; its largest city is neighboring Moline.Rock Island County is one of the four counties that make up the Davenport-Moline-Rock Island, IA-IL Metropolitan Statistical Area.HistoryRock Island County was formed in 1831 out of Jo Daviess County. It was named for Rock Island, an island in the Mississippi River now known as Arsenal Island. GeographyAccording to the U.S. Census Bureau, the county has a total area of, of which is land and (5.2%) is water.Climate and weatherIn recent years, average temperatures in the county seat of Rock Island have ranged from a low of in January to a high of in July, although a record low of was recorded in February 1996 and a record high of was recorded in July 2006. Average monthly precipitation ranged from in January to in June.