Rock County, Minnesota: History
The county was established on May 23, 1857, by an act of the territorial legislature, although it was not organized at that time. Originally, the area was designated as Pipestone County, and the name Rock County was given to what is now Pipestone County. However, in 1862, the Minnesota state legislature changed the designations, assigning the present names to the respective counties. On March 5, 1870, the state legislature passed an act that finalized the organization of Rock County and designated Luverne as its county seat. The county derived its name from the Rock River, which was named after a prominent rocky outcrop referred to as "The Rock" on an 1843 map of the area. This outcrop is composed of reddish-gray quartzite and is located approximately 3 miles (4.8 km) north of Luverne. The mound stands out dramatically amidst the surrounding low prairie. Another source suggests that the county's name is attributed to its rocky soil.