The England–Wales border, sometimes referred to as the Wales–England border or the Anglo-Welsh border, runs for 160 miles from the Dee estuary, in the north, to the Severn estuary in the south, separating England and Wales. It has followed broadly the same line since the 8th century, and in part that of Offa’s Dyke; the modern boundary was fixed in 1536, when the former marcher lordships which occupied the border area were abolished and new county boundaries were created. The administrative boundary of Wales was confirmed in the Local Government Act 1972. Whether Monmouthshire was part of Wales, or an English county treated for most purposes as though it were Welsh, was also settled by the 1972 Act, which included it in Wales.