Lewistown is a city in Lewis County, Missouri, United States. The population was 534 at the 2010 census. It is part of the Quincy, IL–MO Micropolitan Statistical Area. It is located on state highway 6 and near the junction of state highway 6 and state highway 16. Lewistown is in the Lewis County C-1 school district. The nearby Lewis County Fair Grounds are the site of the annual Lewis County Agricultural Fair.