Following the Norman Conquest of 1066, York was substantially damaged by the punitive harrying of the north (1069) launched by William the Conqueror in response to regional revolt. Two castles were erected in the city on either side of the River Ouse. In time York became an important urban centre as the administrative centre of the county of Yorkshire, as the seat of an archbishop, and at times in the later 13th and 14th centuries as an alternative seat of royal government. It was an important trading centre. Several religious houses were founded following the Conquest, including St Mary's Abbey and Holy Trinity Priory. The city as a possession of the crown also came to house a substantial Jewish community under the protection of the sheriff.