The Rock River is a tributary of Rock River Bay, an arm of Missisquoi Bay in the northern part of Lake Champlain. The river rises in the town of Franklin, in Franklin County, Vermont, United States, flows west into the town of Highgate, Vermont, and then north into Saint-Armand, Quebec, in the Brome-Missisquoi Regional County Municipality, administrative re…The Rock River is a tributary of Rock River Bay, an arm of Missisquoi Bay in the northern part of Lake Champlain. The river rises in the town of Franklin, in Franklin County, Vermont, United States, flows west into the town of Highgate, Vermont, and then north into Saint-Armand, Quebec, in the Brome-Missisquoi Regional County Municipality, administrative region of Montérégie, in the southwest of the province of Quebec, Canada. The river then turns south and re-enters Highgate, flowing into Rock River Bay north of Highgate Springs.