Wisconsin does allow double towing but there are restrictions.
(i) A 3-vehicle combination consisting of a towing vehicle and, in order by weight, with the lighter of the towed vehicles as the 3rd vehicle in the 3-vehicle combination unless not structurally possible, a recreational vehicle or camping trailer as the 2nd vehicle, and a recreational vehicle, camping trailer, or trailer carrying any vehicle for recreational use or carrying no load as the 3rd vehicle may, without a permit, be operated on a highway if the overall length of the combination of vehicles does not exceed 65 feet and, if the total weight, including any load, of all towed vehicles exceeds 3,000 pounds, one of the towed vehicles is equipped with brakes. No 3-vehicle combination may operate under this paragraph if highway or weather conditions include heavy snow, freezing rain, icy roads, high winds, limited visibility, or upon a highway that is closed or partially closed by the department due to highway conditions.
(j) A 3-vehicle combination not exceeding 70 feet in overall length may, without a permit, be operated on a highway if the towing vehicle serving as the power unit is equipped with a 5th wheel and kingpin connection by which the 2nd vehicle in the 3-vehicle combination is drawn, the 2nd vehicle in the 3-vehicle combination is a recreational vehicle or camping trailer, including any combination camping-horse trailer, the 3rd vehicle in the 3-vehicle combination is a recreational vehicle or camping trailer or a trailer carrying any vehicle for recreational use, carrying equestrian equipment and equestrian supplies for recreational purposes, or carrying no load, and, if the total weight, including any load, of all towed vehicles exceeds 3,000 pounds, one of the towed vehicles is equipped with brakes. No 3-vehicle combination may operate under this paragraph if highway or weather conditions include heavy snow, freezing rain, icy roads, high winds, limited visibility, or upon a highway that is closed or partially closed by the department due to highway conditions.