Heixiazi Island is called Mowuzhu Island in Manchu, which originally meant "horse head". The island is located at the confluence of the Heilongjiang (Amur) River and Wusuli (Ussuri) River on the Sino-Russian border. It is also known as the Fuyuan Delta, with an area of about 300 square kilometers.
During the Qing Dynasty, after the Second Opium War when the Qing was defeated, Tsarist Russia forced the Qing government to sign the "Sino-Russian Treaty of Aigun", seizing about 630,000 square kilometers of land north of the Heilongjiang River. In 1860, Tsarist Russia again forced the signing of the "Treaty of Beijing", demarcating the eastern section of the Sino-Russian border along the Heilongjiang and Wusuli Rivers, ceding the territory north of the Heilongjiang River and east of the Wusuli River to Russia.