Lewistown is a city in Lewis County, Missouri, United States. The population was 595 at the 2000 census, at which time it was a town. 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.