The town was proclaimed in 1913 and named after Bastiaan Koster, the original farm owner. Koster means "bellringer".
Town 58 km south-west of Rustenburg and 72 km west-north-west of Magaliesburg. It was founded on the farm Kleinfontein in 1913, and has been administered by a village council since January 1931. Said to have been named either after Dr Herman Jacob Coster (1866-1899), State Attorney of the South African Republic, after its surveyor, or after Bastiaan Hendricus Koster, owner of the farm Kleinfontein. The latter explanation seems most plausible.