Des Groseilliers, a coureur de bois ("runner of the woods"), worked with the Jesuit missionaries among the Hurons near Lake Huron in the 1640s. From 1654 to 1656 he explored what is now northern Ontario, and was one of the first to reach Lake Superior. The natives told him of the vast fur-trading areas to the north and west of the lake, around Hudson Bay. In 1659, with fellow coureur de bois Pierre-Esprit Radisson (whose sister des Groseilliers had married), returned to the area and brought back thousands of furs. The officials in New France, however, who were opposed to the independent spirit of the coureurs de bois, confiscated their furs and arrested them for trading without a license.
In 1669 they defected to the English and led them, in the ship Nonsuch, into Hudson Bay from the north, bypassing the land route from New France. After this successful expedition, the English founded the Hudson's Bay Company in 1670.
Both Radisson and des Groseilliers were considered traitors by the French, but unlike Radisson, des Groseilliers was eventually allowed to return to New France. He helped lead raids against his former English allies, destroying many of their new trading posts along Hudson Bay. He died in New France in 1696.