Northwood, situated in the London Borough of Hillingdon, is a leafy residential settlement adjoining the ancient Ruislip Woods. Originally a small hamlet, the population had risen to 2,500 by the early 1900s, and has continued to grow since, its transport connections to the capital making it a popular with commuters. The extension of the Metropolitan Railway from 1904 saw an increasing number of travellers in search of a day out drawn to the area.Northwood's buildings and geology are also of much interest, with the area home to many cave shafts, and chalk used in the construction industry. This has left its mark on the architecture of many buildings and farmhouses, many of which feature in Northwood Through Time. Today, the population has reached 13,000, yet Northwood has retained its leafy, countryside feel.