[3] According to the United States Census Bureau, the township has a total area of 34.1 square miles (88.4 km2), all land.

The city of Coates is at the northwest corner of Vermillion Township.

As of the census[1] of 2000, there were 1,243 people, 395 households, and 325 families residing in the township.

The racial makeup of the township was 97.51% White, 0.16% African American, 0.32% Native American, 0.16% Asian, 0.08% Pacific Islander, 1.13% from other races, and 0.64% from two or more races.

12.7% of all households were made up of individuals, and 3.3% had someone living alone who was 65 years of age or older.