The island of Saint Martin is technically known as both Saint-Martin and Sint Maarten; it all depends on where you're standing. The northern part of the island, which is an overseas collectivity of France, is Saint-Martin. Upon crossing the boundary into the Dutch side of the island, you have entered Sint Maarten.
The 34-square mile island was split in 1648 with the signing of the Treaty of Concordia. Though the Dutch side accounts for only 39% of the island, it is more heavily populated. As of 2009, there were nearly 41,000 inhabitants in Sint Maarten compared to the almost 37,000 residents on the French side.
In addition to the name, there are other differences between the north and south side of the island. While the entire island is a popular vacation destination, the Dutch side is known for its casinos and nightlife, whereas the French side is popular for high-end shopping.