In the late thirteenth century, Italian Marco Polo wrote a book about his travels in Asia. He had traveled there on lengthy overland routes but gained special attention by returning part of the way by sea. In his book, he proclaimed the riches of the "Indies"—a general and vague geographic term encompassing India, China, and countries of the Far East. The well-circulated book played a major role in inspiring European merchants and explorers in later decades to search for a shorter sea route to these lands that produced such an array of luxury goods and spices.

Approximately one hundred years later, a Portuguese prince who came to be known as Henry the Navigator added to the enthusiasm by supporting voyages of discovery and settlement to islands in the Atlantic such as Madeira, the Canaries, and the Azores...