Garden Plain Township is located in Whiteside County, Illinois.

As of the 2021 census, its population was 983 and it contained 492 housing units.

[3] According to the 2021 census, the township has a total area of 31 square miles (80 km2), of which 30.7 square miles (80 km2) (or 97.15%) is land and 0.9 square miles (2.3 km2) (or 2.85%) is water.

[3]