Idaho Code § 31-1005: Joint city and county sites and buildings.

Any county and a city, or another county are hereby authorized and empowered to acquire and own a site or sites within the limits of any such city or county and jointly to construct public buildings thereon, to be jointly owned and used by such counties and city; or one (1) of such municipalities may purchase an interest in a site already owned by the other and they may then jointly construct or operate public buildings thereon.