Charlestown Township was organized in 1872, and named for Charles Porter, a pioneer settler.

As of the census[1] of 2000, there were 217 people, 86 households, and 70 families residing in the township.

The racial makeup of the township was 98.16% White, 0.46% Pacific Islander, and 1.38% from two or more races.

12.8% of all households were made up of individuals, and 2.3% had someone living alone who was 65 years of age or older.

About 4.1% of families and 6.8% of the population were below the poverty line, including 10.6% of those under the age of eighteen and 8.0% of those 65 or over.