Lewistown (also Lewis Town or Lewiston) is an unincorporated community in central Washington Township, Logan County, Ohio, United States. Until the 1829 Treaty of Lewistown, the community was the site of a Shawnee settlement known by the same name, named after Shawnee leader Captain John Lewis. Nearby Indian Lake was once known as the Lewistown Reservoir, after this settlement. Although it is unincorporated, it has a post office, with the ZIP code of 43333. The population of the ZCTA for ZIP code 43333 was 693 at the 2000 census.