Historic Diaries: Marquette and Joliet
September 1673: Chicago to Milwaukee
St. Cosme's anecdote is on pages 337-361 of "The Voyage of St. Cosme, 1698-1699" at American Journeys. His remark at the end, that "Many travellers have already been wrecked there", suggests that perhaps more trips were made by French traders and priests than were documented in the written record (unless he refers to Indian travellers).
During the third week of September, 1673, Marquette and Joliet made their way along the Lake Michigan shore north of Chicago. Marquette wrote no notes about it, but the difficulties along this stretch of Lake Michigan were described by Fr. Jean St. Cosme, who canoed it in October of 1698. It's safe to assume that Marquette and Joliet encountered similar conditions a generation earlier, since they were traveling at roughly the same time of year as St. Cosme:
St. Cosme's Report: "On the eleventh of October we started early in the morning from the fort of Milouakik [Milwaukee], and at an early hour we reached Kipikaoui [modern Racine, Wisconsin], about eight leagues farther. Here we separated from Monsieur de Vincenne's party, which continued on its route to the Miamis.
"Some savages had led us to hope that we could ascend this river [the Root River] and after a portage of about two leagues might descend by another river called Pesioui [Fox River, in northeastern Illinois] which falls into the River of the Illinois about 25 or 30 leagues from Chikagou, and that we should thereby avoid all the portages that had to be made by the Chikagou route. We passed by this river [Root] which is about ten leagues in length to the portage. We remained five days at Kipikaoui [Racine], leaving on the 17th and after being windbound on the 18th and 19th we camped on the 20th at a place five leagues from Chikagou.
"We should have arrived there early on the 21st but the wind which suddenly arose on the lake compelled us to land half a league from Chikagou. We had considerable difficulty in landing and in saving our canoes; we all had to jump into the water.
"One must be very careful along the lakes, and especially Lake Mixcigan, whose shores are very low, to take to the land as soon as possible when the waves rise on the lake, for the rollers become so high in so short a time that one runs the risk of breaking his canoe and of losing all it contains. Many travellers have already been wrecked there."