Formed in 1882 from part of Rush Township, it is named for Warren Delano Jr., maternal grandfather of Franklin Delano Roosevelt, 32nd President of the United States, 1933–1945.

According to the U.S. Census Bureau, the township has a total area of 8.2 square miles (21 km2), all land.

As of the census[4] of 2000, there were 487 people, 210 households, and 152 families residing in the township.

There were 224 housing units at an average density of 27.3 per square mile (10.5/km2).

24.3% of all households were made up of individuals, and 12.9% had someone living alone who was 65 years of age or older.