 King 's Highway 89 , commonly referred to as Highway 89 , is an east – west provincially maintained highway in the southwestern portion of the Canadian province of Ontario , stretching 107 kilometres ( 66 mi ) from the junction of Highway 9 and Highway 23 in Harriston in the west , to Highway 400 just east of Cookstown in the east . The principal urban centres along the highway include Alliston , Shelburne and Mount Forest . Outside of these towns , the highway travels through rural farmland across a large part of southwestern Ontario . 
