Witt is a city in Montgomery County, Illinois, United States. The population was 785 at the 2020 census, down from 903 in 2010. Witt is in easter…Witt is a city in Montgomery County, Illinois, United States. The population was 785 at the 2020 census, down from 903 in 2010. Witt is in eastern Montgomery County along Illinois Route 16, which leads 11 miles southwest to Hillsboro, the county seat, and 4.5 miles northeast to Nokomis.