Niles is a city in Berrien and Cass counties in the U.S. state of Michigan, near the Indiana state line city of South Bend. The population was 11…Niles is a city in Berrien and Cass counties in the U.S. state of Michigan, near the Indiana state line city of South Bend. The population was 11,988 according to the 2020 census. It is the larger, by population, of the two principal cities in the Niles-Benton Harbor metropolitan area, an area with 153,797 people.