Holt is an unincorporated community and census-designated place in Ingham County in the U.S. state of Michigan. The CDP is located within Delhi Charter Township and occupies a majority of the township. The population was 25,625 at the 2020 census, which is a significant increase from 11,315 at the 2000 census when the CDP area was significantl…Holt is an unincorporated community and census-designated place in Ingham County in the U.S. state of Michigan. The CDP is located within Delhi Charter Township and occupies a majority of the township. The population was 25,625 at the 2020 census, which is a significant increase from 11,315 at the 2000 census when the CDP area was significantly smaller.