Most of the Champagne vineyard area is located in the French department of Marne.
The Marne department contains the major centers of Reims and Épernay and includes several of Champagne’s best-known vineyard zones, such as the Montagne de Reims, the Vallée de la Marne, and the Côte des Blancs. Together, these areas account for the largest concentration of vines within the appellation.
Champagne’s protected production area also extends into the departments of Aube, Aisne, Haute-Marne, and Seine-et-Marne. The Aube, in particular, is an important southern wine-producing area, centered on the Côte des Bar. It is therefore incorrect to treat Champagne as a single small district around Reims, even though Marne is its dominant department.
Department boundaries and wine subregions are different kinds of geography. A vineyard zone can cross administrative boundaries, while the Champagne appellation is defined by legally delimited communes and production rules. Marne is the administrative answer, not the name of the entire appellation.