Virginia is a city and the county seat in Cass County, Illinois, United States. The population was 1,514 at the 2020 census. According to t…Virginia is a city and the county seat in Cass County, Illinois, United States. The population was 1,514 at the 2020 census. According to the 2021 census gazetteer files, Virginia has a total area of 1.27 square miles, of which 1.21 square miles is land and 0.06 square miles is water.