As of the 2020 census, its population was 4,467 (up from 4,094 at 2010[3]) and it contained 1,814 housing units.

[4] Johnson Township was organized in 1823.

[5] According to the 2010 census, the township has a total area of 40.64 square miles (105.3 km2), of which 40.53 square miles (105.0 km2) (or 99.73%) is land and 0.11 square miles (0.28 km2) (or 0.27%) is water.

[3] The township contains four cemeteries: Nobles, Powell, Stunkel, Tabor and Williams.

Johnson Township is served by the South Gibson School Corporation.