Brown County was established August 25, 1855. In the 1870s, the secretary of the state Board of Agriculture attempted to determine for whom the county was named. Several of the legislators in the 1855 session declared the Brown County was named for Albert Gallatin Brown (1813-1880), United States senator from Mississippi at the time of the Kansas-Nebraska Act. Other legislators, however, stated it was named for O. H. Browne, a member of that legislature. The county name was spelled Browne in the original statute, but the county seal omitted the 'e', as have all subsequent statutes.
County Seat is Hiawatha.