[3] According to Warren Upham, the origin of the name Leenthrop is uncertain but probably Swedish.

[3] According to the United States Census Bureau, the township has a total area of 35.7 square miles (92 km2), of which 35.7 square miles (92 km2) is land and 99.93% is water.

As of the census[1] of 2000, there were 396 people, 99 households, and 79 families residing in the township.

There were 104 housing units at an average density of 2.9 per square mile (1.1/km2).

19.2% of all households were made up of individuals, and 8.1% had someone living alone who was 65 years of age or older.