Tazewell County is located in the U.S. state of Illinois. According to the 2020 census, it had a population of 131,343. Its county seat and largest city is Pekin. It is pronounced with a short "a", to rhyme with "razz" rather than "raze." Tazewell County is part of the Peoria, IL Metropolitan Statistical Area. The majority of the population lives along the county's western border.