The New Road was a toll road built across fields around the northern boundaries of London, the first part of which opened in 1756. The route comprises the following modern-day roads: Old Marylebone Road, Marylebone Road, Euston Road, Pentonville Road, City Road, and Moorgate.
In the 18th century London began to grow rapidly. Until 1750 there was only one road crossing over the Thames, namely London Bridge. But the capital started to sprawl, first along the river from the City to Westminster, and then north past Soho (in medieval times, the king's hunting grounds) to Oxford Street and beyond.
The Proceedings of the Old Bailey Online Project give a good overview of the demographic growth of the capital. From the early 19th century, London was the largest city in the world.