Frenchman Samuel de Champlain had explored the area extensively in 1605. He had specifically explored Plymouth Harbor, which he called "Port St. Louis," and he made an extensive and detailed map of it and the surrounding lands. He showed the Patuxet village (where the town of Plymouth was later built) as a thriving settlement. However, an epidemic wiped out up to 90 percent of the Indians along the Massachusetts coast in 1617–1619, including the Patuxets, before the arrival of the "Mayflower". The epidemic has traditionally been thought to be smallpox, but a recent analysis has concluded that it may have been a lesser-known disease called leptospirosis. The absence of any serious Indian opposition to the Pilgrims' settlement may have been a pivotal event to their success and to English colonization in America.