Before 1659
There have been many territorial changes in the Pyrenees in the centuries preceding the Treaty of the Pyrenees of 1659. In most cases, the Pyrenees proved to be a natural border between territorial entities north and south. As far as we know there were no systematic delimitations by bordermarkers.

Some treaties are important in this respect:
- 1258 Treaty of Corbeil: the kingdoms of France and Navarra settled their division in the eastern Pyrenees, the border shifted to the north of the current Pyrénées-Orientales.
- 1278 and 1288 Signing of the first and second "Paréage" of Andorra, which arranged the joint sovereignty of Andorra by the Count of Foix and the bishop of Urgell. That's how Andorra came into existence.
- 1375 Junte de Roncal: a local treaty between the communities of the Baŕetous valley and the Roncal valley on either side of the esfr-border on and near Col de Saint-Martin (bm262). Following two years of mutual bloodshed, the conflict about access to the only watersource on this dry plateau (at the Spanish side of Pic d'Arlas) was settled. The yearly ceremony on 13 july of the "Tribut de trois vaches" still exists.
- 1462-1493 Treaty of Bayonne: a temporary shift of Rousillon and Cerdagna from Navarra to France in exchange for military aid to help Navarra in the Catalonian civil war.
- 1513 "Le serment de Plan d'Arrem": a local treaty about cross-border use of pastures, forests, sources, transport and mutual help between 19 French and Spanish communities in a wide area around Fos where the treaty was signed. There were more of such local "Lies and passeries" in the Pyrenees, providing stability and peace in these borderregions. In the Bayonne demarcation treaties (1856-1868) some of them were incorporated.
1641 Treaty of Péronne: giving the king of France the title of count of Barcelona,  Cerdagne and Roussillon while these territories remained under the jurisdiction of Catalonia.

1659: Treaty of the Pyrenees
Louis XIV of France and Philippe IV of Spain agreed to this treaty to end their 1635-1659 war.   It was signed on an island in the river Bidassoa near Hendaye, exact at the border. Known as the "l'Île des Faisans" (and later "l'Île de la Conférence") it was transformed in a condominium: a shared territory between France and Spain.

Fixating the border in the Pyrenees was only a part of this broad-range treaty. However: the description of the borderline remained very vague. Article 42 states that the mountains of the Pyrenees will divide the two kingdoms as it did between de French and Spanish tribes in the Roman era. 

However, a specification of the borderline was discussed in March 1660 in Céret by Spanish and French deputies. Roussilion was lost by Spain  The Cerdagne was divided, a division settled in the Treaty of Llivia of 1660. Thirty-two villages became French but Llivia - considered as a town - remained Spanish and turned into an enclave in autumn 1660. There's no mention whatsoever of bordermarkers.  

1764: Convention of Perpignan
South of Perpignan - at and near the Col de Perthus - France and Spain didn't agree about the exact borderline to be established after the treaty of the Pyrenees. France claimed for historical reasons a strip of territory south of the watershed as shown approximately on this map with a blue line. After a century, France gave in and the borderline was fixed as it is still today. 

The treaty involved the placing of 10 bordermarkers:
- 2 pillar-like markers with a coat of arms of both countries at either side of the main road from Perpignan passing through the Col de Perthus into Spain (nowadays bm574 and 575) 
- 4 pyramid-shaped markers around the Fort de Bellegarde to the west (nowadays bm567, 568, 570 and 571)
- 4 pyramid-shaped markers to the east (nowadays bm576, 577, 578 and 579).

In 1866 these markers were restored and incorporated in the 1 to 602 number sequence.

1785: Treaty of Elizonda: settling the Pays Quint disputes
In 1785 there was a first attempt to precisize the esfr-borderline in the Treaty of Elizonda. Two French and Spanish military engineers (the "Commision Internationale Caro-d'Ornano") were assigned with this job.
This treaty was primarily meant to settle the border-disputes in the valleys south of Saint-Étienne-de-Baïgorry. The so-called "ligne d'Ornano" - two straight lines neglecting the watershed - was established as the border in the valley of Baïgorry.  This line is first from bm130 straight to bm141 at the hilltop of Ichterbegui and from there to bm155 at Col de Lindus. There were special cross-border rules for the French and Spanish shepherds and peasants. But the disputes went on. In the end, this culminated in 1856 in a special status for the part south of the Ornano-line: "le pays Quint". See esfr-html-curiosities.html 

The treaty was accompanied by a "procés-verbal" describing 197 - unnumbered - borderstones and -crosses from Col d'Ispéguy (current bordermarker 91) to Col d'Arnostéguy (current bm205).
In fact, there were two "procès-verbaux":
1. (between august 29th and september 8th 1785) describing the 162 bordermarkers from 'Beorzu' until Col d'Arnostéguy ( from west to east)
2. (september 21th and 22th 1785) describing the 35 bordermarkers from 'Beorzu' until Col d'Izpeguy (from east to west).

The demarcation-job E of Pays Quint was however suspended in 1792 or 1793, due to the political situation and the difficulties encountered in the mountainous terrain (see this article)