In Russia and the Soviet Union, the boundary along the Kuma–Manych Depression was the most commonly used as early as 1906. In 1958, the Soviet Geographical Society formally recommended that the boundary between Asia and Europe be drawn in textbooks from Baydaratskaya Bay, on the Kara Sea, along the eastern foot of the Ural Mountains, then following the Ural River until the Mugodzhar Hills, and then the Emba River; and Kuma–Manych Depression, thus placing the Caucasus entirely in Asia and the Urals entirely in Europe. However, most geographers in the Soviet Union favoured the boundary along the Caucasus crestE. M. Moores, R. W. Fairbridge, Encyclopedia of European and Asian regional geology, Springer, 1997, , p. 34: "most Soviet geographers took the watershed of the Main Range of the Greater Caucasus as the boundary between Europe and Asia." and this became the standard convention in the latter 20th century, although the Kuma–Manych boundary remained in use in some 20th-century maps.
