The board of county commissioners when authorized to erect any county building or joint county and municipal building shall have power to acquire ground for a site by purchase or condemnation. The board shall also have the entire supervision of the construction of all county buildings and monuments. Source: SL 1897, ch 49 , § 4; RPolC 1903, § 973; RC 1919, § 6985; SDC 1939, § 12.2307.