Litchfield is a city in Montgomery County, Illinois, United States. The population was 6,605 at the 2020 census. It is located in South Central Illinois, south of Springfield, Illinois, and part of the Metro Eas…Litchfield is a city in Montgomery County, Illinois, United States. The population was 6,605 at the 2020 census. It is located in South Central Illinois, south of Springfield, Illinois, and part of the Metro East of St. Louis.