Pillager is a city in Cass County, Minnesota, United States. Its population was 507 at the 2020 census. It is part of the Brainerd Micropolitan St…Pillager is a city in Cass County, Minnesota, United States. Its population was 507 at the 2020 census. It is part of the Brainerd Micropolitan Statistical Area. A post office called Pillager has been in operation since 1886. The city was named after the Pillager Band of Chippewa Indians.