The first inhabitants of the islands were probably a group of Dutch colonists who made their home on Providencia towards the end of the 16th century. In 1631 they were expelled by the English, who effectively colonized the islands. The English brought with them African slaves from Jamaica and began to cultivate tobacco and cotton. The Raizal people are the product of intermingling between these colonizers and their slaves. The Spanish, irate at the English success on the islands, unsuccessfully invaded the archipelago in 1635.
Because of their strategic location, the islands provided convenient shelter for pirates waiting to sack Spanish galleons bound for home, laden with gold and riches. In 1670 legendary pirate Henry Morgan established his base on Providencia, and from here he raided both Panama and Santa Marta. Legend has it that his treasures are still hidden somewhere on the island.
Shortly after Colombia achieved independence in 1810, it laid claim to the islands, although Nicaragua fiercely disputed its right to do so. The issue was eventually settled by a treaty in 1928, which confirmed Colombia's sovereignty over the islands.
Geographic isolation kept the islands' unique Anglo-Caribbean character virtually intact, though things started to change when a flight service connected the islands to mainland Colombia in the 1950s. In 1954 a government plan to make the islands a duty-free zone brought with it tourism, commerce, entrepreneurs and Colombian culture, which slowly began to uproot the 300-year-old Raizal identity, pushing it aside in favor of big tourism bucks.
In the early 1990s the local government introduced restrictions on migration to the islands in order to slow the rampant influx of people and to preserve the local culture and identity. Yet Colombian mainlanders account for two-thirds of San Andrés' population, and English and Spanish have been the two official languages since 1991.
The tourist and commercial boom has caused San Andrés to lose much of its original character; it's now a blend of Latin American and Anglo-Caribbean culture, though there is a movement to restore Raizal roots on the island. Providencia has preserved much more of its colonial culture, even though tourism is making inroads into the local lifestyle, and you'll hear Spanish spoken just as commonly as (if not more than) the traditional English dialect that had, until recently, always predominated.
Although the political status of San Andrés and Providencia is unlikely to change, Nicaragua continues to press the issue of its sovereignty over the islands at the International Court of Justice in The Hague. The court reaffirmed Colombia's sovereignty over the main islands in 2007, and over its maritime boundary and secondary islands in 2012.