Fillmore is a town in Marion Township, Putnam County, in the U.S. state of Indiana. The population was 532 at the 2020 census. The town is part of the South Putnam Community Schools school district. An old variant name of the community was called Nicholsonville. A post office was established under this name in 1849, and was renamed to Fillmore in 1861, wher…Fillmore is a town in Marion Township, Putnam County, in the U.S. state of Indiana. The population was 532 at the 2020 census. The town is part of the South Putnam Community Schools school district. An old variant name of the community was called Nicholsonville. A post office was established under this name in 1849, and was renamed to Fillmore in 1861, where it is still currently operating.