Ralls County is a county located in the northeastern portion of the U.S. state of Missouri. As of the 2020 census, the population was 10,355. Its county seat is New London. The county was organized November 16, 1820, and named for Daniel Ralls, Missouri state legislator. Ralls County is part of the Hannibal, MO Micropolitan Statistical Area, which is also included in the Quincy-Hannibal, IL-MO Combined Statistical Area.