Arkhangelsk Oblast eventually spread well beyond the Arkhangelsk Region. The Mezen horses, bred in the Mezen River valley, are rather small but suitable for difficult work and easily survive cold winters. The area of current Arkhangelsk Oblast has always been located on the trading routes connecting central Russia to the White Sea, and, in fact, in the 17th century the White Sea was the main sea export route for Russia. The whole course of the Northern Dvina is navigable, as well as the lower course of some of its tributaries, most notably the Vychegda, the Vaga, and the Pinega. The Mezen is
Arkhangelsk Oblast the 1970s and is expected to become part of the Belkomur project — a railway line connecting Arkhangelsk via the Komi Republic with the Perm Krai and the Ural mountains. Almost the entire rail network belongs to the Northern Railway, which west of Onega connects to the Oktyabrskaya Railway. There is also a railway line from Severoonezhsk west to Yangory (an extension of the line from Puksa to Navolok), which belongs to the Department of Corrections. A big number of narrow gauge railways have been built in the 1950s and 1960s to facilitate the transport of timber, but since then