Around 1700 a party of pirates operated out of a cave-hideout on Hermit Island, in Wisconsin, preying on trappers, traders and passenger ships. In 1705 they attacked a party of French traders and all of the pirates were killed. It is believed that their plundered valuables were secreted somewhere in the area of the cave and never recovered.
Treasure of Fort Crawford
Eighty thousand dollars in gold coins, earmarked as payroll for outposts and military forts in 1832, was buried during an Indian attack on Fort Crawford at Prairie du Chien in Wisconsin. The coins were buried by a detail of soldiers from the fort "on the highest bluff across from the fort. In four piles. Each 20,000." The soldiers who hid the payroll were killed before returning to the fort and the gold was never recovered.