Monroe Township is one of the twelve townships of Preble County, Ohio, United States. The 2000 census found 2,290 people in the township, 1,314 of whom lived in the unincorporated portions of the township.GeographyLocated in the northern part of the county, it borders the following townships: Butler Township, Darke County - northTwin Township, Darke County - northeast cornerHarrison Township - eastTwin Township - southeast cornerWashington Township - southJackson Township - southwest cornerJefferson Township - westHarrison Township, Darke County - northwest corner Two incorporated villages are located in Monroe Township: Eldorado in the northwest, and West Manchester in the northeast.Name and historyMonroe Township was established in 1817. It is one of twenty-two Monroe Townships statewide.