While Hadrian's Wall ran from Wallsend on the Tyne to Bowness-on-Solway, there were further installations to both east and west. West of Bowness, the pattern of milecastles and turrets (here called mile-fortlets and towers), but with no linear barrier, was continued down the coast for at least 40km. Several forts were also built along the coast. Later, a fort was erected at South Shields overlooking the mouth of the River Tyne.
There were also at least three forts to the north of the Wall. These all lay to the west. behind the wall lay a network of forts, spreading to the southern limits of the Pennines where lay the legionary bases of York and Chester. It seems probable that the legionary legate at York, as a senior army officer of senatorial rank, had some overall responsibility for the auxilliary units in the North, including those on the Wall.