High Quality Content by WIKIPEDIA articles! King`s Highway 21, commonly referred to as Highway 21, is a provincially maintained highway in the Canadian province of Ontario that begins at Highway 402 mid-way between Sarnia and London and ends at Highway 6, Highway 10 and Highway 26 in Owen Sound. The roadway is referred to as the Bluewater Highway because it remains very close to the eastern shoreline of Lake Huron.