Wis. Stat. § 347.09: Headlamps on motor vehicles.

(1) No person may operate a motor vehicle on a highway during hours of darkness or during a period of limited visibility, unless the vehicle is equipped as follows:

(a) Except as provided in pars. (b) and (c), every motor vehicle shall be equipped with at least 2 headlamps, which headlamps shall comply with the requirements and limitations set forth in sub. (2) and s. 347.10 and shall be mounted symmetrically with respect to the vertical plane extending through the longitudinal axis of the vehicle with at least one on each side of the center of the front of the motor vehicle.

(b) Every moped or motorcycle shall be equipped with at least one and not more than 2 headlamps, which headlamps shall comply with the requirements and limitations set forth in sub. (2) and s. 347.10.

(c) Every motor bicycle or vehicle registered under s. 341.067 and operated by a person licensed under s. 343.075 or 343.135 shall be equipped with at least one and not more than 2 headlamps, which headlamps shall comply with the requirements and limitations set forth in sub. (2) and s. 347.11.

(2) Every headlamp on a motor vehicle shall be located at a height of not more than 54 inches nor less than 24 inches.