New Plymouth, OhioNew Plymouth is an unincorporated community in northwestern Brown Township, Vinton County, Ohio, United States. It has a post office with the ZIP code 45654. It is located at the intersection of State Routes 56 and 328.HistoryA post office has been in operation at New Plymouth since 1850. New Plymouth was named after Plymouth, Massachusetts, the native home of a large share of the early settlers.TourismRavenwood Castle is a unique country inn located on Bethel Road in New Plymouth, Ohio.