[3][4] In December 1871, Hugh P. McClymonds and Samuel L. Riddle leased fifteen acres of land to two brothers from the Cooper family.

As more speculators became interested in McClymonds' property, however, discord arose between competitors; in response, McClymonds sold the entire property, with the except of its farm buildings and fourteen acres of surface land, for $60,000 on June 18 of that same year to Karns, O. G. Emery, John H. Haines, William Parker, and William Thompson.

[5] In short order, the few buildings grew to several and then many, with entrepreneurs adding hotels, livery stables, machine shops, residences, and restaurants to turn the small, rural village into a booming town that soon became known as Karns City.

[6] The borough of Karns City, which included all of McClymonds' land and roughly ten acres owned by Riddle, was subsequently incorporated on January 4, 1875.

[6] Karns City is located in eastern Butler County at 40°59′42″N 79°43′33″W / 40.995048°N 79.725743°W / 40.995048; -79.725743,[7] in the valley of the South Branch of Bear Creek, a tributary of the Allegheny River.

According to the United States Census Bureau, Karns City has a total area of 0.36 square miles (0.94 km2), all land.