The Russian Empire was a state that existed from 1721 until the Russian Revolution of 1917. It was the successor to the Tsardom of Russia, and the predecessor of the Soviet Union. It was the second largest contiguous empire the world had seen. At one point in 1866, it stretched from eastern Europe, across northern Asia, and into North America.
At the beginning of the 19th century, Russia was the largest country in the world, extending from the Arctic Ocean to the north to the Black Sea on the south, from the Baltic Sea on the west to the Pacific Ocean on the east. Across this vast realm were scattered the Emperor's 150 million subjects, who represented a great disparity in economic, ethnic, and religious positions.