Treaty of York

The Treaty of York was an agreement between the kings Henry III of England and Alexander II of Scotland, signed at York on 25 September 1237, which affirmed that Northumberland (which at the time also encompassed County Durham),^[1] Cumberland, and Westmorland were subject to English sovereignty. This established the Anglo-Scottish border in a form that remains almost unchanged to modern times (the only modifications have been regarding the Debatable Lands and Berwick-upon-Tweed).^[2] The treaty detailed the future status of several feudal properties and addressed other issues between the two kings, and historically marked the end of the Kingdom of Scotland's attempts to extend its frontier southward.

The treaty was one of a number of agreements made in the ongoing relationship between the two kings. The papal legate Otho of Tonengo was already in the Kingdom of England at Henry's request, to attend a synod in London in November 1237. Otho was informed in advance by Henry of the September meeting at York, which he attended. This meeting was recorded by the contemporary chronicler Matthew Paris, who disparaged both Alexander and Otho.