Wis. Const. art. XIII, § 9

All county officers whose election or appointment is not provided for by this constitution shall be elected by the electors of the respective counties, or appointed by the boards of supervisors, or other county authorities, as the legislature shall direct. All city, town and village officers whose election or appointment is not provided for by this constitution shall be elected by the electors of such cities, towns and villages, or of some division thereof, or appointed by such authorities thereof as the legislature shall designate for that purpose. All other officers whose election or appointment is not provided for by this constitution, and all officers whose offices may hereafter be created by law, shall be elected by the people or appointed, as the legislature may direct.