Spaniards thought that Bonaire could be used as a cattle plantation worked by natives. The cattle were raised for hides rather than meat. The Spanish inhabitants lived mostly in the inland town of Rincon which was safe from pirate attack. Dutch period The Dutch West India Company was founded in 1621. Starting in 1623, ships of the West India Company called at Bonaire to obtain meat, water and wood. The Dutch also abandoned some Spanish and Portuguese prisoners there, and these people founded the town of Antriol, which is a contraction of Spanish al interior (English: inside). The Dutch and the Spanish fought from 1568 to 1648 in what is now known as the Eighty Years War. In 1633, the Dutch having lost the island of St. Maarten to the Spanish retaliated by attacking Curaçao, Bonaire and Aruba. Bonaire was conquered in March 1636. The Dutch built Fort Oranje in 1639. While Curaçao emerged as a centre of the slave trade, Bonaire became a plantation of the Dutch West India Company. Salt became a major export product of the island; a small number of African slaves were put to work alongside Indians and convicts, cultivating dyewood and maize and harvesting solar salt around Blue Pan. Slave quarters, built entirely of stone and too short for a man to stand upright in, still stand in the area around Rincon and along the salt pans. The slave population grew in the 1710s when a famine and social unrest on Curaçao caused the Dutch to relocate a large number of slaves to Bonaire. Historically, Dutch was not widely spoken on the island outside of colonial administration; its use increased in the late 19th and early 20th centuries. Students on Curaçao, Aruba and Bonaire were taught predominantly in Spanish until the late 18th century when the British took Curaçao, Aruba and Bonaire; the teaching of Spanish was restored when Dutch rule resumed in 1815. During the Napoleonic Wars, the Netherlands lost control of Bonaire twice, once from 1800 to 1803, and again from 1807 to 1816. During these intervals, the British had control of the neighbouring island of Curaçao and of Bonaire. The ABC islands were returned to the Netherlands under the Anglo-Dutch Treaty of 1814. During the period of British rule, a large number of white traders settled on Bonaire, and they built the settlement of Playa (Kralendijk) in 1810. Emancipation From 1816