The southeast corner of Siberia south of the Stanovoy Range was twice contested between Russia and China. Hydrologically, the Stanovoy Range separate the rivers that flow north into the Arctic from those that flow south into the Amur River.  Ecologically, the area is the southeastern edge of the Siberian boreal forest with some areas good for agriculture. Socially and politically, from about 600 AD, it was the northern fringe of the Chinese-Manchu world. Various Chinese dynasties would claim sovereignty, build forts and collect tribute when they were strong enough.  The Ming dynasty Nurgan Regional Military Commission built a fort on the Northern bank of the Amur at Aigun, and established an administrative seat at Telin, modern Tyr, Russia above Nikolaevsk-on-Amur. Russian expansion into Siberia began with the conquest of the Khanate of Sibir in 1582.  By 1643 they reached the Pacific at Okhotsk. East of the Yenisei River there was little land fit for agriculture, except Dauria, the land between the Stanovoy Range and the Amur River which was nominally subject to the Qing dynasty. In 1643, Russian adventurers spilled over the Stanovoy Range, but by 1689 they were driven back by the Qing. The land was populated by some 9,000 Daurs on the Zeya River, 14,000 Duchers downstream and several thousand Tungus and Nivkhs toward the river mouth. The first Russians to hear of Dauria were probably Ivan Moskvitin and Maxim Perfilev about 1640. In 1859/60 the area was annexed by Russia and quickly filled up with a Russian population.. What was annexed by Russia in 1859/60?