The effect on Salford of the Industrial Revolution has been described as "phenomenal". The area expanded from a small market town into a major industrial metropolis; factories replaced cottage industries, and the population rose from 12,000 in 1812 to 70,244 within 30 years. By the end of the 19th century it had increased to 220,000. Large-scale building of low quality Victorian terraced housing did not stop overcrowding, which itself led to chronic social deprivation. The density of housing was as high as 80 homes per acre. Private roads were built for the use of the middle classes moving to the outskirts of Salford. The entrances to such roads, which included Elleray Road in Irlams o' th' Height, were often gated, and patrolled.