Adopted 6 June 1922, as labelled on BC map 1EM, 1915, referring to the plateau between Osoyoos, Rock Creek and Sidley.

Source: BC place name cards, or correspondence to/from BC's Chief Geographer or BC Geographical Names Office

Anarchist Mountain and Sidley were both named after Richard G. Sidley, an early settler and first postmaster at Sidley (1895), who, because he showed some brilliance, was appointed Justice of the Peace and Customs Officer (dates not cited). He held, for his time, somewhat advanced political views; he was often called an anarchist, and this plateau became known locally as "the anarchist's mountain". Local officialdom eventually relieved him of his posts. (Rupert W. Haggen, BCLS, Origin of Place Names in Boundary District, 1945 manuscript, file H.1.45.)

Source: BC place name cards, or correspondence to/from BC's Chief Geographer or BC Geographical Names Office

After Richard G. Sidley, a wild Irishman who arrived in the Osoyoos district around 1889. His extreme political views ultimately resulted in cancellation of his appointments as JP and Customs officer at Sidley. Before the anarchist came to the Okanagan, this mountain was known as Larch Tree Hill.

Source: Akrigg, Helen B. and Akrigg, G.P.V; British Columbia Place Names; Sono Nis Press, Victoria 1986 /or University of British Columbia Press 1997