Brown County is a county located in the northeast portion of the U.S. state of Kansas. Its county seat and most populous city is Hiawatha. As of the 2020 census, the county population was 9,508. The county was named after Albert G. Brown, a U.S. Senator from Mississippi and Kansas statehood advocate. The Kickapoo Indian Reservation of Kansas, the majority of the Sac and Fox Reservation, and the majority of the Iowa Reservation of Kansas and Nebraska are located within the county.