Elgin is a city in Cook and Kane counties in the U.S. state of Illinois. It is located 35 mi northwest of Chicago along the Fox River. As of the 20…Elgin is a city in Cook and Kane counties in the U.S. state of Illinois. It is located 35 mi northwest of Chicago along the Fox River. As of the 2020 census, the city had a population of 114,797, making it the sixth-most populous city in the state.