The county has an area of 1,263 km (488 sq mi) and a population of 911,403. The population is concentrated in the east, the area closest to Greater London, which includes the county's largest towns: Reading (174,224), Slough (164,793), Bracknell (113,205), and Maidenhead (70,374). The west is rural, and its largest town is Newbury (33,841). For local government purposes Berkshire comprises six unitary authority areas: Bracknell Forest, Reading, Slough, West Berkshire, Windsor and Maidenhead, and Wokingham. The historic county included the parts of Oxfordshire south of the River Thames, which formed its northern border, but excluded Caversham and Slough.