Carthage is a city in and the county seat of Hancock County, Illinois, United States. Its population was 2,490 as of the 2020 census. Carthage is best known for being the site of the 1844 death of Joseph Smith, who founded the Latter Day Saint movement.

Hancock County is a county in the U.S. state of Illinois. According to the 2020 census, it has a population of 17,620. Its county seat is Carthage, and its largest city is Hamilton. The county is composed of rural towns with many farmers.