Question: When did the Portuguese explore the Gold Coast of the region where Daniel Houghton died?

full_context: Document 1: Obaysch: Obaysch (1849? – 11 March 1878) was the first hippopotamus seen in Great Britain since prehistoric times, and the first in Europe since Ancient Rome. He was captured on an island on the White Nile when he was less than one year old. His name is derived from the name of the island.
Document 2: Portugal: Portugal spearheaded European exploration of the world and the Age of Discovery. Prince Henry the Navigator, son of King João I, became the main sponsor and patron of this endeavour. During this period, Portugal explored the Atlantic Ocean, discovering several Atlantic archipelagos like the Azores, Madeira, and Cape Verde, explored the African coast, colonized selected areas of Africa, discovered an eastern route to India via the Cape of Good Hope, discovered Brazil, explored the Indian Ocean, established trading routes throughout most of southern Asia, and sent the first direct European maritime trade and diplomatic missions to China and Japan.
Document 3: Republic of the Congo: The Portuguese explorer Diogo Cão reached the mouth of the Congo in 1484. Commercial relationships quickly grew between the inland Bantu kingdoms and European merchants who traded various commodities, manufactured goods, and people captured from the hinterlands. After centuries as a major hub for transatlantic trade, direct European colonization of the Congo river delta began in the late 19th century, subsequently eroding the power of the Bantu societies in the region.
Document 4: Spice trade: The first country to attempt to circumnavigate Africa was Portugal, which had, since the early 15th century, begun to explore northern Africa under Henry the Navigator. Emboldened by these early successes and eyeing a lucrative monopoly on a possible sea route to the Indies the Portuguese first crossed the Cape of Good Hope in 1488 on an expedition led by Bartolomeu Dias. Just nine years later in 1497 on the orders of Manuel I of Portugal, four vessels under the command of navigator Vasco da Gama rounded the Cape of Good Hope, continuing to the eastern coast of Africa to Malindi to sail across the Indian Ocean to Calicut, on the Malabar Coast. in south India -- the capital of the local Zamorin rulers. The wealth of the Indies was now open for the Europeans to explore; the Portuguese Empire was the earliest European seaborne empire to grow from the spice trade.
Document 5: Hartog Plate: Hartog Plate or Dirk Hartog's Plate is either of two plates, although primarily the first, which were left on Dirk Hartog Island during a period of European exploration of the western coast of Australia prior to European settlement there. The first plate, left by Dutch explorer Dirk Hartog, is the oldest-known artifact of European exploration in Australia still in existence. The original dish was returned to the Netherlands where it is on display in the Rijksmuseum. A replacement and additional dish were subsequently discovered on three additional visits over the next 200 years
Document 6: Middle Ages: In the early 15th century, the countries of the Iberian peninsula began to sponsor exploration beyond the boundaries of Europe. Prince Henry the Navigator of Portugal (d. 1460) sent expeditions that discovered the Canary Islands, the Azores, and Cape Verde during his lifetime. After his death, exploration continued; Bartolomeu Dias (d. 1500) went around the Cape of Good Hope in 1486 and Vasco da Gama (d. 1524) sailed around Africa to India in 1498. The combined Spanish monarchies of Castile and Aragon sponsored the voyage of exploration by Christopher Columbus (d. 1506) in 1492 that discovered the Americas. The English crown under Henry VII sponsored the voyage of John Cabot (d. 1498) in 1497, which landed on Cape Breton Island.
Document 7: European colonisation of Southeast Asia: The spice trade was made possible by the maritime trade route. In 1498, the Portuguese navigator, Vasco da Gama, sailed round the Cape of Good Hope and opened up a sea route from Europe to India. Bringing home samples of exotic oriental products, da Gama greatly increased European interest in the new trade route and the new trade route quickly facilitated the expansion of trade. Eventually, the Dutch wrestled control of it from the Portuguese in the 17th century, and in the 18th century, the British gained control of it from the Dutch. Nevertheless, the spice route greatly increased trading activities, deepened the economic relations between Europe and Southeast Asia and as a result, more European merchants found their way to Southeast Asia.
Document 8: Mungo Park (explorer): Mungo Park (11 September 1771 -- 1806) was a Scottish explorer of West Africa. He was the first Westerner known to have travelled to the central portion of the Niger River, and his account of his travels is still in print.
Document 9: Daniel Houghton: Daniel Houghton (1740–1791) was an Irish explorer and one of the earliest Europeans to travel through the interior of West Africa.
Document 10: European exploration of Africa: European exploration of Sub-Saharan Africa begins with the Age of Discovery in the 15th century, pioneered by Portugal under Henry the Navigator. The Cape of Good Hope was first reached by Bartolomeu Dias on 12 March 1488, opening the important sea route to India and the Far East, but European exploration of Africa itself remained very limited during the 16th and 17th centuries. The European powers were content to establish trading posts along the coast while they were actively exploring and colonizing the New World. Exploration of the interior of Africa was thus mostly left to the Arab slave traders, who in tandem with the Muslim conquest of the Sudan established far - reaching networks and supported the economy of a number of Sahelian kingdoms during the 15th to 18th centuries.
Document 11: History of the Cape Colony before 1806: The written history of the Cape Colony in what is now South Africa began when Portuguese navigator Bartolomeu Dias became the first modern European to round the Cape of Good Hope in 1488. In 1497, Vasco da Gama sailed along the whole coast of South Africa on his way to India, landed at St Helena Bay for 8 days, and made a detailed description of the area. The Portuguese, attracted by the riches of Asia, made no permanent settlement at the Cape Colony. However, the Dutch East India Company (VOC) settled the area as a location where vessels could restock water and provisions.
Document 12: Cumberland Gap: In 1775 Daniel Boone, hired by the Transylvania Company, arrived in the region leading a company of men to widen the path through the gap to make settlement of Kentucky and Tennessee easier. On his arrival Boone discovered that Martin had beaten him to Powell Valley, where Martin and his men were clearing land for their own settlement -- the westernmost settlement in English colonial America at the time. By the 1790s the trail that Boone and his men built had been widened to accommodate wagon traffic and sometimes became known as the Wilderness Road.
Document 13: Daniel O'Connell (journalist): Daniel O'Connell (1849 – 23 January 1899) was a poet, actor, writer and journalist in San Francisco, California, and a co-founder of the Bohemian Club. He was the grand-nephew of Daniel O'Connell (1775–1847), the famed Irish orator and politician.
Document 14: Portuguese discoveries: Portuguese discoveries (Portuguese: Descobrimentos portugueses) are the numerous territories and maritime routes discovered by the Portuguese as a result of their intensive maritime exploration during the 15th and 16th centuries. Portuguese sailors were at the vanguard of European overseas exploration, discovering and mapping the coasts of Africa, Canada, Asia and Brazil, in what became known as the Age of Discovery. Methodical expeditions started in 1419 along West Africa's coast under the sponsorship of prince Henry the Navigator, with Bartolomeu Dias reaching the Cape of Good Hope and entering the Indian Ocean in 1488. Ten years later, in 1498, Vasco da Gama led the first fleet around Africa to India, arriving in Calicut and starting a maritime route from Portugal to India. Portuguese explorations then proceeded to southeast Asia, where they reached Japan in 1542, forty - four years after their first arrival in India. In 1500, the Portuguese nobleman Pedro Álvares Cabral became the first European to discover Brazil.
Document 15: Portuguese discovery of the sea route to India: One of the sailors, Bartolomeu Dias passed the southernmost point of Africa known as the Cape of Good Hope in 1488. He declared it possible to travel to India by going around Africa. The Portuguese were then able to make an immense profit by using their own ships to retrieve the spices.
ground_truth: 15th century
sub_queries: Daniel Houghton >> place of death Answer: West Africa
when did the portuguese explore the gold coast of West Africa Answer: 15th century