Between 1627 and 1631, Holland decided to send settlers to St. Martin, to exploit the island's natural salt reserves. The French and the Dutch signed the Treaty of Concordia, also known as the Partition Treaty, on March 23, 1648. So the island was split into two parts and shared by France and Holland.

The island of Saint Martin is unique for being the smallest inhabited landmass in the world shared by two nations: France and the Netherlands. The division dates back to the Treaty of Concordia, signed on March 23, 1648. Before this, both nations, along with the Spanish, had interests in the island due to its valuable salt ponds and strategic location. After the Spanish abandoned their claim, the French and Dutch settlers decided to divide the island rather than fight over it. Legend has it that the border was determined by a walking contest: a Frenchman and a Dutchman started at the same point and walked in opposite directions around the coast until they met; the French ended up with more territory (the northern side, Saint-Martin) supposedly because the Frenchman drank wine which energized him, while the Dutchman drank jenever (gin) which slowed him down. In reality, the French had a larger naval presence nearby, which likely influenced the negotiation. Today, there is no physical border or "hard" customs between the two sides, allowing for a seamless blend of French elegance and Dutch Caribbean liveliness.