The Côtes-d'Armor, formerly known as Côtes-du-Nord until 1990, is a department in the north of Brittany, in northwestern France. In 2019, i…The Côtes-d'Armor, formerly known as Côtes-du-Nord until 1990, is a department in the north of Brittany, in northwestern France. In 2019, it had a population of 600,582. Côtes-du-Nord was one of the original 83 departments created on 4 March 1790 following the French Revolution. It was made up from the near entirety of the ancient Pays de Saint-Brieuc, most of historical Trégor, the eastern half of Cornouaille, and the north-western part of the former diocese of Saint-Malo.