Argonne, a mountainous and wooded region of X. E. France, forming a part of French Lorraine and Champagne, extending along the rivers Meuse and Aisne nearly 47 m. from Sedan (Ardennes) to beyond Ste. Menehould (Marne). It is bounded N. by the Ardennes and S. by the Meuse mountains, and contains many forests and ranges with several almost inaccessible passes. W. Argonne, or the Ar-gonne forest proper, a wooded elevation 800 to 900 ft. high, extends over 30 m., with a breadth varying from 1 to 8 m., from the sources of the Aisne, along that river and the Meuse northward as far as Chene-Popu-leux, separating the fertile plains from the barren steppes between Vitry and Sezanne, familiarly called Champagne Pouilleuse. The forest of E. Argonne, 600 to 900 ft. high, including in the N. the forest of Apremont, 1,225 ft. high, runs parallel with W. Argonne along the E. bank of the Meuse. The forest of Argonne contains several defiles renowned in history, among them the battlefield of Valmy, and has therefore been called the French Ther-mopylae. Several important military movements and actions took place within its limits during the Franco-German war of 1870, preceding the battle of Sedan.