The reason why the island is split into two different territories is because the French and Dutch both coveted the island. While the French wanted to colonize the islands between Trinidad and Bermuda, the Dutch found San Martín a convenient halfway point between their colonies in New Amsterdam (present day New York) and Brazil. The Dutch got there first, easily founding a settlement there in 1631 due to the very low population and erecting Fort Amsterdam as protection from invaders, and Jan Claeszen Van Campen became it's first governor, with the Dutch West India Company beginning its salt mining operations on the territory. French and British settlements also started popping up on the island.
Spain soon attacked and captured Saint Martin in 1633 in The Eighty Years' War, kicking out most of the colonists who were already there. At Point Blanche, they built what is now Old Spanish Fort to secure the territory. However, they soon abandoned the territory in 1648 due to St. Martin barely turning a profit and the war ending, resulting in them no longer needing a base in the Caribbean. Both the Dutch and the French jumped at the chance to re-establish their settlements. Dutch colonists came from St. Eustatius, while the French came from St. Kitts. After some initial conflict, however, both sides realized that neither were willing to give up, and rather than have an all-out war, they signed the Treaty of Concordia in 1648, which divided the island in two. However, despite the treaty, relations between the two sides were not always good, with the entire island coming under effective French control from 1795 when Netherlands became a puppet state under the French Empire until 1815 and up to 16 border conflicts occurring between 1648 and 1816.
Slavery was a huge issue there, due to the huge number of slaves brought there to work on cotton, tobacco and sugar plantations and the cruel treatment of the slaves by their masters, and the slaves staged rebellions with their huge numbers making it impossible to ignore. The French abolished slavery in their colonies in 1848, including the French side of St. Martin, which led to slaves on the Dutch side of the island protested and threatened to flee to the French side to seek asylum and forced the local Dutch authorities to free the colonies' slaves, though it was not until 1863 when the Dutch abolished slavery in all of their island colonies that the slaves became legally free.
With the abolition of slavery, Sint Maarten began focusing on tourism in the 1950s instead of plantation work, with Saint Martin following suit two decades later. The tourist boom was heavier on Sint Maarten than Saint Martin and the surrounding islands, however, and its Princess Juliana International Airport became one of the busiest in the Eastern Caribbean. The territory also got a huge immigration boom from the neighbouring Lesser Antilles, Curaçao, Haiti, the Dominican Republic, the United States, Europe and Asia, too.
The Sint Maartener flag