 In 1862 the Minnesota state legislature changed the designations, attaching the present names to the present counties.On March 5, 1870, the state legislature approved an act that finalized the county's organization and designated Luverne as the county seat.The county's name came from the Rock River, which in turn is named for a prominent rocky outcrop (designated "The Rock" on an 1843 map of the area) of reddish-gray quartzite, about 3 miles (5 km) north of Luverne.