Jasper County is a county located in the U.S. state of Illinois. According to the 2020 census, it has a population of 9,287. Its county seat is Newton. Jasper County was formed in 1831 out of Clay and Crawford Counties. It was named for Sgt. William Jasper, a Revolutionary War hero from South Carolina. During the defense of Fort Moultrie in 1776, the staff of the …Jasper County is a county located in the U.S. state of Illinois. According to the 2020 census, it has a population of 9,287. Its county seat is Newton. Jasper County was formed in 1831 out of Clay and Crawford Counties. It was named for Sgt. William Jasper, a Revolutionary War hero from South Carolina. During the defense of Fort Moultrie in 1776, the staff of the American flag was shot away. Sgt. Jasper attached the flag to a pole and stood on the wall waving the flag at the British until a new staff was erected.