What is the oldest border in Europe?

The border between Portugal and Spain, largely fixed by the Treaty of Alcañices in 1297, is usually called the oldest in Europe.

When was the England-Scotland border set?

The Treaty of York in 1237, between Henry III of England and Alexander II of Scotland, set the border roughly where it is today. The town of Berwick-upon-Tweed kept changing hands until 1482.

Where was the Treaty of the Pyrenees signed?

On Pheasant Island in the Bidasoa river, on the French-Spanish border, in 1659. The island is shared: France and Spain take turns governing it for six months at a time.

Borders drawn by two kings.

Most borders are the result of wars, uprisings and endless arguments. A few of Europe's oldest were settled in a single treaty between two crowns, and have barely moved in centuries.

A Timeless Tales story · 4 minute read

The short version, from my channel. Watch it on YouTube.

England and Scotland: York, 1237

For decades Scottish kings claimed the northern English counties of Northumberland, Cumberland and Westmorland. In 1237 Henry III of England and Alexander II of Scotland settled it in the Treaty of York: Scotland gave up the claim, and the border was fixed roughly along the line between the Solway Firth and the River Tweed, close to where it runs today.

It was not quite the end. The town of Berwick-upon-Tweed changed hands more than a dozen times in the wars that followed, and only became English for good in 1482.

Portugal and Spain: Alcañices, 1297

In 1297 King Denis of Portugal and King Ferdinand IV of Castile signed the Treaty of Alcañices. It set the line between the two kingdoms, and most of it has stayed put ever since, which is why it is usually called the oldest border in Europe.

There is one sore spot: the town of Olivenza, taken by Spain in 1801. Spain governs it as Olivenza; Portugal has never formally accepted that and still calls it Olivença.

France and Spain: an island in a river, 1659

The long war between France and Spain ended with the Treaty of the Pyrenees, signed in 1659 on Pheasant Island, a tiny island in the Bidasoa river on the border. It was negotiated by the chief ministers of the two kings, Cardinal Mazarin and Don Luis de Haro. Spain gave France Roussillon and part of Cerdanya, and the border was drawn along the Pyrenees.

The kings themselves, Louis XIV and Philip IV, met on the same island in 1660, when Louis married Philip's daughter. Two odd legacies remain. Pheasant Island is still shared: France and Spain take turns governing it, six months at a time. And the treaty handed France the villages of Cerdanya, but Llívia counted as a town, so it stayed Spanish. It is still a small piece of Spain completely surrounded by France.

1237 Treaty of York: England and Scotland
1297 Treaty of Alcañices: Portugal and Castile
1482 Berwick-upon-Tweed becomes English for good
1659 Treaty of the Pyrenees, on Pheasant Island
1801 Spain takes Olivenza

Sources

Treaty of York, Wikipedia
Treaty of Alcañices, Wikipedia
Treaty of the Pyrenees, Wikipedia
Pheasant Island, Wikipedia
Llívia, Wikipedia