Route 143 is a north/south highway on the south shore of the Saint Lawrence River. Until the mid-1970s when the province decided to renumber all highways other than autoroutes, it was known as Route/Highway 5. Its northern terminus is in Saint-François-du-Lac, at the junction of Route 132, and the southern terminus is in Stanstead at the border with Vermont where the road continues past the Derby Line-Stanstead Border Crossing as U.S.