For a quick and dirty biography of the guy who "discovered" Lake Superior, check out this link from a Canadian historian. We mostly know Etienne Brule from the lovely rivers named after him: the Brule River in Judge Magney State Park (which disappears into the Devil's Kettle), and the Brule River east of Superior, where there is great canoeing and trout fishing.
Brule's journey to Lake Superior led all over the eastern seaboard, including the Ohio and Potomac rivers. Brule went totally wild, adopting the dress and language of the Hurons. He could not be kept under the control of Champlain. It turns out Brule was a renegade, and, eventually, the victim of cannibals.