Vermilion County is a county located in the eastern part of the U.S. state of Illinois, between the Indiana border and Champaign County. It was established in 1826 and was the 45th of Illinois' 102 counties. According to the 2010 census, it had a population of 81,625, which is a decrease of 2.7% from 83,919 in 2000. It contains 21 incorporated settlements; the county seat and largest city is Danville.