As of the 2020 census, its population was 759 (a tiny decline of 760 from 2010[4] The township was named for the large amount of timber it contained at the time it was organized.

After the completion of the "Clover Leaf" railroad through the area in 1874 and the establishment of the town of Forest along it, residents petitioned the county commissioners to create a new township for their area out of the existing Johnson and Warren townships.

On January 2, 1882, the petition was granted and the township organized with Samuel M. Davis as the first trustee.

The arrival of pioneers here was somewhat later than in other parts of the county since Forest was originally within the Big Miami Reserve and off limits to white settlement until 1838.

A post office was established in 1860 in the hamlet of Martinsville, with Martin Davis as the first postmaster.