If you love maps like me, then you’ve come to the right page!

For this project, I have compiled a vast collection of stunning historical maps. For now, I have uploaded just a few important ones, but more maps will be coming in the future as I expand this website. I also hope to create a custom map that will depict the actual routes used by Moncacht-Apé during his journey across North America. In the meantime, here are some historical maps that are crucial to the investigation.

In upper left corner of the above map, Le Page attempts to depict the route of Moncacht-Apé during his late-1600s journey to the Pacific. The Yazoo explorer’s descriptions of his route are quite clear. He explains that his course across the West generally followed a heading between “the cold,” or generally north, and “the setting sun,” or generally west. This indicates a general northwesterly route, allowing for local deviations when following river bends or diverting around mountainous topography.

My investigation reveals that Moncacht-Apé’s descriptions of his route across the unmapped West were a much better match for the Platte River (which is not depicted in the above map) and two of its major tributaries. Conversely, his descriptions clearly do not match the Missouri River. The upper courses of both rivers would not be accurately determined until decades after Le Page published Moncacht-Apé’s account and this map. 

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A Mix-up in River Names

In both of the above maps, the Missouri River is depicted with a strikingly incorrect course. In reality, the Missouri makes two extended jogs to the north. Instead, the “Missouri River” that’s depicted by Le Page in 1757, and which was based upon his interview with Moncacht-Apé, is given a generally northwesterly course that’s more similar to the Platte River and two of its principal tributaries, the North Platte and Sweetwater Rivers.

You can compare the true courses
of the Missouri and Platte Rivers
using this watershed map on Wikipedia.

That Moncacht-Apé would have followed the Platte route makes a lot of sense for multiple reasons. For one thing, during U.S. settlement of the West, the Platte-North Platte-Sweetwater corridor would become the preferred route for overland migration to the West. In time, the route would be called the Oregon Trail, which few Americans would remember was based upon an Indigenous trade route that existed for centuries.

Lewis and Clark ascended the Missouri River in boats because they were looking for a mythical Northwest Passage, an interior water route to the Pacific that did not exist. Moncacht-Apé was a friendly interpreter who went on foot. He conversed extensively with local tribes, so he would have learned there was a better overland route to follow. As the Yazoo explorer progressed west, the tribes spoke different languages, and some likely used different names for the various rivers. The river names Moncacht-Apé learned during his journey would not necessarily match the river names that later became common in the French colonies to the east.

Furthermore, my ongoing investigation has turned up numerous historical maps from the 1700s that depict the Missouri River with a northwesterly course more similar to the Platte River. Occasionally, some 1700s maps give the Missouri a somewhat more accurate course that includes some northerly segments and bends. It’s important to note that the upper courses of both rivers remained unknown to white Europeans, including the French and Americans, until the Lewis and Clark Expedition explored the Louisiana Purchase in 1804 to 1806.

These prior 1700s maps were mostly created by distant cartographers based upon details provided by informants. Sometimes this information came directly to the cartographers during interviews, but more often it was second-hand information being passed by intermediaries. Most of the initial informants were Natives and some fur trappers. Some of these informants may have lived in or visited parts of the little-known West, but often the informants themselves were relaying second-hand information that they had learned from others. Either way, the informants typically shared geographic details during visits to the frontier settlements of Europeans and Americans, such as St. Louis in the present-day state of Missouri.

Given this backstory, there are plausible reasons for a mix-up when naming which of these two major but unmapped rivers Moncacht-Apé had followed during a long journey made about thirty years before his 1720s interview with Le Page.

Soon I will have much more to share about this part of the mystery!