Brown County (county code BR) is a county in the northeast part of the U.S. state of Kansas. In 2010, 9,984 people lived there. Its county seat is Hiawatha. Hiawatha is the second-biggest city in Brown County. Brown County is where the Kickapoo Indian Reservation of Kansas is. It also has most of the Sac and Fox Reservation and most of the Iowa Reservation of Kansas and Nebraska.