In 1800 the arrondissements of Arras, Béthune, Boulogne, Montreuil and Saint-Omer were established. The arrondissement of Saint-Pol was created in 1801, and disbanded in 1926.[3] In 1962 the arrondissement of Calais was created from part of the arrondissement of Boulogne-sur-Mer, and the arrondissement of Lens from part of the arrondissement of Béthune.[3][4] In January 2007 the arrondissement of Arras lost the canton of Le Parcq to the arrondissement of Montreuil, and the two cantons of Avion and Rouvroy to the arrondissement of Lens.[3]
The borders of the arrondissements of Pas-de-Calais were modified in January 2017:[5]
three communes from the arrondissement of Arras to the arrondissement of Béthune
eight communes from the arrondissement of Arras to the arrondissement of Lens
one commune from the arrondissement of Boulogne-sur-Mer to the arrondissement of Calais
one commune from the arrondissement of Lens to the arrondissement of Béthune
23 communes from the arrondissement of Saint-Omer to the arrondissement of Calais