There are 7 US Post Offices in Brown County serving a total of 10,010 residents equating to 1,430 residents per post office. It's estimated that approximately 15,977 packages are handled across the 7 county post offices annually. Brown County (county code BR) is a county located in the northeast portion of the U.S. state of Kansas. As of the 2010 census, the county population was 9,984. Its county seat and most populous city is Hiawatha. Brown County is the location of 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."