Treaty of Aigun
In ancient times the area was inhabited by the Donghu, the Xiongnu, the Xianbei, the Khitan, and the Mongols. During the decline of China's last dynasty, the Russian Empire forced the house of Qing (1644–1912) to cede the Outer Manchurian territory in the 1858 Treaty of Aigun. That treaty effectively made the Argun River, which originates in this area, the border between China and Russia.