In the 17th century, Swedish slave traders started to become involved with the Atlantic slave trade. Between 1784 and 1878, Sweden maintained possession of a handful of colonies in the Caribbean. The Swedish colony of Saint Barthélemy functioned as a duty-free port and became a major destination center for slave ships. Slaves were brought in tax free by foreign vessels and the Swedish Crown made a profit by collecting an export tax when slaves were shipped out. Sweden was also a major supplier of iron chains used in the slave trade. In the early 19th century, Sweden signed treaties with the United Kingdom and France to abolish the slave trade.