Some of the cities, towns, and places in Jersey County are Beltrees, Brighton, Chautauqua, Delhi, Dow, East Newbern, Elsah, Elsah Township, English Township, Fidelity, Fidelity Township, Fieldon, Grafton, Jersey Township, Jerseyville, Kemper, Lake Piasa, Lockhaven, McClusky, Mississippi Township, New Delhi, Newbern, Nutwood, Otter Creek Township, Otterville, Piasa Township, Quarry Township, Reardon, Reddish, Richwood Township, Rosedale, Rosedale Township, Ruyle Township, Spankey
Jersey County is a county located in the U.S. state of Illinois. At the 2020 census, it had a population of 21,512. The county seat and largest community is Jerseyville, with a population of 8,337 in 2010. The county's smallest incorporated community is Otterville, with a population of 87.
Jersey County is included in the St. Louis, MO-IL Metropolitan Statistical Area.