County Derry dates from the time of the Plantation of Ulster, when lands to the west of the now extinct county of Coleraine were joined to it to form the modern county. It is bounded by Lough Foyle to the west, the Sperrin Mountains to the south and the River Bann to the east. Sean McMahon's history starts with a consideration of the county's topography. The hills at the south and centre have tended to cut off the Foyle Basin from the east and cause the gaze of Derry City to turn towards Donegal and the west. Likewise, the east of the county around Coleraine tends to look east towards Antrim, Belfast and Scotland. The east-west division is also marked by a preponderance of Protestant population in the east and Catholic in the west. The earliest discovered settlement in all of Irish history - Mount Sandel on the lower Bann - is in County Derry, dating to almost 6,000 b.c. In medieval times the site of the modern city was an important monastic centre associated with St Colmcille. The modern county begins its life with the Plantation, but it was the Industrial Revolution, bringing textile workers into Derry City from County Donegal, that effected the greatest transformation. Derry, which had hitherto been a walled Protestant town at the margin of the Plantation settlement, gradually acquired a Catholic majority whose political and national ambitions were frustrated by partition. The mixture of poverty and frustration that resulted eventually brought about the civil rights clashes of October 1968 that are generally reckoned to mark the start of the modern Troubles. Bloody Sunday in January 1972 was probably the single most notorious incident in the Troubles. Sean McMahon's history deals with all these public events, whilst celebrating the social and educational traditions and accomplishments of the city and county.