when did london's population reach 1 million
History of London During the 19th century, London was transformed into the world's largest city and capital of the British Empire. Its population expanded from 1 million in 1800 to 6.7 million a century later. During this period, London became a global political, financial, and trading capital. In this position, it was largely unrivalled until the latter part of the century, when Paris and New York began to threaten its dominance.