Brenton County was split off from Braxton County in 1877. Much of the county initially comprised of land west of the Colruona. The county line was extanded east in the 1880s and 1890s, and in 1899 the westernmost portion was split off to form Dillon County.
The largest city and county seat is Montillo (which extends into Dillon County). Other towns include:
- Brack (also in Elgin County)