In the early 19th century, following the exclusion of Canadian traders from U.S. territories after the War of 1812, the fur trade on the island came under the control of the American Fur Company, founded by John Jacob Astor in 1808. This trade was managed by the "South West Company", the Midwestern division of the Astor company. Before 1830 Astor had established a monopoly on the fur trade in the United States. Having made millions, he left the trade before it declined and started to invest in real estate in New York and other cities. The island's fur trading history has been preserved in the Madeline Island Historical Museum.