The Russian Empire, also known as Imperial Russia or simply Russia, was a vast realm that spanned most of northern Eurasia from its proclamation in November 1721 until its dissolution in March 1917. At its height in the late 19th century, it covered an area of approximately 22,800,000 square kilometres , roughly one-sixth of the world's landmass, making it the third-largest empire in history, surpassed only by the British and Mongol empires; it also held colonies in North America between 1799 and 1867. It had a population of 125.6 million in 1897, per the only census conducted during the entire imperial period, which featured considerable ethnic, linguistic, religious, and socioeconomic diversity.