As of the 2020 census, its population was 747 (down from 802 at 2010[4]) and it contained 323 housing units.

Harrison Township was organized in 1836.

[5] It was named for William Henry Harrison, who had served as Governor of the Indiana Territory, congressman, senator, and who would afterward serve as the ninth President of the United States.

[6] Harrison Township covers an area of 35.49 square miles (91.9 km2), all land.

The township contains four cemeteries: Crooked Creek, Grant, Old Indian Creek and Saint Elizabeth.