Porte des Morts, also known as Porte des Mortes, the Door of Death, and Death's Door is a strait linking Lake Michigan and Green Bay between the northern tip of the Door Peninsula and the southernmost of the Potawatomi Islands. At its narrowest reach between Plum Island and the peninsula, the Porte des Morts Passage is about one and one third miles across. The name is French and means "door of the dead".
Current dynamics
North of the peninsula, warm water from Green Bay flows into Lake Michigan on the surface, while at the same time, cold lakewater enters Green Bay deep underneath.
Origin of the name
According to traditions given by the Native Americans to area fishermen in the 1840s and reported both by Captain Brink, a government engineer who surveyed the area in 1834, and by Hjalmar R. Holand in his two-volume history of Door County, the ominous name is traced back to a battle between the Winnebago and Potawatomi tribes. Holand's report is as follows:
The Winnebago, having migrated from the southwest, were not content to share the land with the gentle Potawatomi, who had arrived before them. They had already pushed the latter from the peninsula to the islands and were preparing to attack the islands, too. The Potawatomi devised a desperate plan for defense. They sent three scouts to spy out the Winnebago positions. The spies were then to light a signal fire so the Potawatomi warriors could land safely and attack the Winnebago from behind. The spies, however, were discovered and captured. Two died with their secret, but one revealed the plan.
Knowing the plan, the Winnebago decided to use it to their advantage and devised a two pronged attack. They chose a high bluff where there was no safe landing and set a signal fire there. There they planned to intercept the war party as they were helpless in their canoes. They sent a second group to attack the villages of the Potawatomi, which would be defenseless with their warriors gone.
When the Potawatomi defenders left the islands, the weather was relatively calm, but by the time they were mid channel, a stiff north wind set in. They pressed on, however, confident that they could land safely near the signal fire. When they arrived, the Winnebago attacked, raining destruction from above. They could not land, and the strong north wind and waves prevented their fleeing to safety. Canoes capsized in the surf and were dashed against the rocks. A few Potawatomi managed to climb to a ledge a short distance above the waves. Some of the Winnebago jumped down to the ledge and fighting continued there until a large wave took them all to their deaths in the lake.
After the battle at the bluff, the remaining Winnebago waited for the return of their second party. The wind and waves that had prevented the Potawatomi from fleeing apparently also caught the Winnebago raiding party. They were never seen again. The Winnebago took it as a sign that they should not try to cross to the islands again, for it was, they concluded, a doorway to death.
The report seems to be biased in favor of the Potawatomi. The Winnebago, or to use their own chosen name the Ho-Chunk, do not describe themselves as fierce. Various historical accounts indicate that it was the Potawatomi who were the newcomers to the area and that the Winnebago had recently suffered greatly at the hands of the Illinois. If this account accurately gives the origin of the name, the battle probably occurred in the mid seventeenth century, shortly after the Potawatomi settled in the area and before the French used the area enough to name the strait.
Other explanations for the origin of the name have been offered. One account involving Native Americans has a tribe building a ring of campfires on thin ice to lure their enemies through the strait overnight. The plan worked and the attackers perished. Another mentions a storm in which canoes were dashed against the rock but mentions no battle. It has also been said that the French, not wanting the English to establish fur trade routes to Wisconsin and other surrounding areas, named the passage to discourage and scare sailors from sailing through the strait. Yet the strait had its name well before the English were coming to the Great Lakes.